Showerthought: I used to build every illustration on one layer, now I do 40 and I'm honestly not sure which way is better | Digital Art Showcase - The Community Guide
40 layers sounds like a lot until you actually need to move one tree 3 pixels left without dragging the whole forest with it. I did the single layer thing for years and it always turned into a mess the second a client said "can you make the sky more blue but keep the mountains the same." The real question is whether you ever go back and merge stuff down, because 40 layers on a finished piece just means you're scared to commit. Maybe it's just me but a file with 6 or 7 solid layers beats 40 tiny ones every time.