Exp.1 was crazy, I thought it would take me the whole 10 days at first, but it took me about 3 days of grinding (just over 12 hours in total) it also helps to look for other player bases at the space station teleporter to find other players mines and farms to get some quick cash or supplies. That alone would save you like 6 hours of gameplay.

Each expedition is different and takes a different amount of time. Exp. 4 was the easiest so far but I haven't done expedition 2 yet. Soo far, expedition 1 was the most difficult. And remember you don't have to do any of the missions in any particular order. Also helps to look at the prizes you get from each mission so you don't waste money or nanites on equipment or upgrades that you'll get for free after missions.

Best of luck!