It took me several months to do my high detail vampire/undead textures in the marketplace, but I didn't have all day, everyday on them. Seams were difficult to deal with, constantly checking and repainting. It was a bit disheartening for sales to peak at Halloween and then tail off steeply afterwards though: don't other people like vampires the rest of the year?:-( Just kidding:-) But to be honest, I didn't make the textures to make millions here at Renderosity, I made them for people who like them, like me. That's all part of the fun. I assume you asked the question because you want to start creating your own content? My advice then would be: just dive in! It doesn't matter how long it takes: you'll be having fun, doing something you enjoy, learning new skills, and maybe even making a bit of spare cash if you choose to sell your creations. What could be better?