When I used to buy a set, I would always build it. And then it would be up for display to remind me of a building technique or just because I liked the way it looked. Slowly over time I began to scavenge pieces from the sets, although I always looked to take a piece from the back or somewhere out of the way when possible. But I told myself I wouldn't destroy the set, I only needed a white 1x 2 tile or a few jumper tiles to help me try something new.
But then I stopped building sets and just started taking pieces directly from the bags to use on my own creations. I would flip through the instructions to see what could be built and how pieces were being layered, but I wouldn't actually snap the parts together.
Finally, I gave up on sets for a while and just began buying bulk brick online or hitting up local garage sales. But with Christmas and Hanukkah around the corner, I'm kind of excited to begin building sets again, there's something about opening and playing with a new toy during the holidays.