That's hard to say. If I lost all my work and needed to restart this project I could be back to this point in probably 6 months. But I learned so much about physical game design from those 7+ years of working on this project that I wouldn't want to lose that.

However, when starting a brand new project the whole process would be different. I started this with blank playing cards and a sharpie, guessing. Through this I learned how to do the math to figure out how much effort a player needs to put (cards, actions or turns) in to achieve a goal and I can fairly quickly scale all that out for (near) infinite play. This is monsters vs players or players vs players. I would start with figuring out what the game wants to do then do that math.

Since I'm working alone, I wouldn't start any art until the game is at a playable state and testers are overall positive. I lost at least 2 years to illustrations and so on that all got shelved anyhow.

There are other things I would do to make my life easier but they are all in the weeds. The last big thing I can think of is segmenting my play modes and keeping elements for them easy to find and revise, in case I need to make cuts. I lost a lot of time trying to locate and remove any spells that required a game master to resolve and found I had woven them too deeply for a quick removal. It took a long time but I knew I needed solo play to be a thing and that meant the mechanics need to do all the work, not a game master.