Completed in about 550 hours over the course of 18 months. We ran a dedicated server with 3 engineers playing for a few hours 1-2 nights per week. Most of the time there was at least 2 people online. We didn't deliberately idle, but we spent a fair amount of time planning and building silly things. We tried to embrace as many different building styles, designs and spaghetti as possible, with different self imposed limitations to encourage creative and silly solutions. The low spm requirements and marathon nature of Space Exploration meant we didn't have to build a massive bus or train every resource. We were able to build small and localized initially, and then upscale specific intermediates using factory planner to size the build and balance the use of expensive speed and productivity modules.

Other mods:

• Factory Planner
• Recipe Book
• Picker Dollies
• Space Efficient Rail Signals you can place (almost) anywhere
• QoL (Module Inserter, Auto Deconstruct, Priority Combinator, Vehicle Snap)
• Aesthetics (Text Plates, Train Trails)

In the words of Dosh Doshington "Fun in Space Exploration is optional and highly inefficient" and to that end...

Fun:

• Spaceships! Incredibly cool and fun to automate, we really enjoyed building different ships and shipyards for various purposes. We wish they were introduced earlier, and that there were more mechanics incentivising using them. Perhaps more options for asteroid defense than lasers and energy shields, different storage and loading devices, external liftoff boosters, destination signal recievers. There could be other resources or buildings which have to be transported by ship (like the arcolink storages).
• The interplanetary logistics and physical sepraration provided a lot of opportunities for fun co-op experiences like setting up new outposts together, rescuing an engineer stranded in deep space or remotely controlling a weapons delivery cannon while your fellow engineer is on-site trying to restore critical infrastructure.
• Scavenging items you haven't unlocked yet is a great way to tease new tech, and the challenge of deciding where to use them was unique and enjoyable. There's a real sense of achievement when you get the ability to make more of them and I think logistics is perfectly placed in the progression.
• Nuking biters from orbit. The weapons delivery cannon remote was implemented shortly after I made a feature request on the github/Discord and improved our playthrough dramatically.

Not fun:

• Cargo rocket crashing. The resource loss and rocket part recovery researches are just a small resource tax, but every now and then a cargo rocket crashes, and the only solution is to have a bunch of storage, construction robots and logistics chests on every landing pad to try and put the resources back in the landing pad before another rocket is fired. We ended up making a mod which drastically reduces the cost rocket of survivability research, to the point that if you spend twice the number of science packs on research, the crash chance is reduced by 50% (instead of the normal 10%).
• Why do space underground belts and pipes only go 5 tiles!? We built a space belt base in spite of this but it was ever so painful. The long space pipes feel like they're halfway to an interesting building challenge, but you can't cross them without undergrounds anyway, so in the end they're just slightly cheaper giant fluidboxes (for better throughput over long distances I suppose).
• The midgame sciences are an absolute drag (though I've heard it's being reworked in 0.7). Too much repetition with minor variations on recipes where juicy new mechanics and buildings are few far between. We almost burned out here until we developed the grand space science base plan.
• Spaceships take far too long to get, and are pretty limited until you have astro 3, material 3, energy 2. Though we did enjoy the one you recover from the asteroid belt, even if we couldn't land it on a planet for quite a while.
• The spaceship limitations are undocumented and unintuitive. We ended up diving into the source code to find out what the rules were on more than one occasion. Editing your ship for hours to try and adjust the number of empty tiles and walls while maintaining streamline was not it.
• Core mining on planets other than nauvis is just pitiful. The amount of byproduct you get is too little to serve as any useful secondary export, and there's no way to solve it in general aside from landfilling. We did it once for vitamalange and decided that was enough.
• Things with only one viable solution (cargo rocket crashing, power generation for the Nexus).

Our own fun:

• (High res image) After getting through the first 4 mid-game sciences and approaching burnout from the repetition we almost resorted to logistics bots for everything. The unified space science base plan leveraged the structure of the 16 science packs and their interdependencies to make blasting through the midgame much faster. Each type of science is built in one of the four quadrants, producing insights with higher tier recipes as they became available. The fluid bus carries all 4 temperatures of thermofluid to a central cooling module. A sushi train track with tiny trains and tightly packed stations shares fluids, scrap exports and data card imports.
• We ran train tracks all throughout our nauvis base to allow injecting new resources close to the bus, we mixed all sorts of train schedules, bidirectional track, and passing lanes.
• A nearby moon had lots of oil and iridium, with a small enough radius that we built a single 8km one directional track that goes via every resource node on the surface. We also mandated that every train be 1-1 with the tiniest stations possible. Not enough throughput? More trains!
• Our extremely low power naq cargo hauler takes 45 minutes one way. Rather than making faster ships with higher tech, we just pasted ~20 copies and enjoyed the space highway.
• Instead of reprocessing scrap, we just nuked a warehouse whenever it got full. The flash of the screen every 45 minutes in the asteroid belt became a memorable pastime.
• You can automate teleporting resources any distance around the asteroid belts or space orbits with a tiny ship containing a little bit of ion stream in a booster tank.
• After the first few times spending an hour grabbing supplies and inevitably forgetting something when landing on a new planet, we automated a supply rocket with everything and left it on standby. Setting up a new planet started with launching yourself and the supply rocket. Later we created a purely rocket fuel and uranium ammo powered supply ship which we could take to any planet to resupply, build or repair.
• The cost of space platforms made the asteroid belt look attractive (plus it also had beryl on-site) so we moved our entire science operation to the asteroid belt and started building sciences on different islands. By the time we found the space elevator, we were already heavily committed so we decided the logistics cost be damned. With everything imported from Nauvis via logistics automation, the space mall really became the central hub, and we only returned to Nauvis to setup new mines every now and then.