Do tubular PVC slip joints loosen over time?

It's been around a year since I re-plumbed the trap for our kitchen sink with tubular PVC, and I found a large puddle of water in our sink base cabinet a few days ago. When I checked the fittings that make up the trap, I was surprised to find that the connection to the sink strainer and several of the slip joints (a dishwasher wye and baffle tee for the disposal)were no longer even finger tight. I'm certain that I tightened these fittings when I installed them. Do these types of fittings loosen up over time, and do I need to check them periodically to prevent leaks? Or is it more likely that they just got bumped and loosened by moving stuff in the sink base cabinet?

It's more likely that they got bumped, but pvc does expand and contract quite a bit as it thermal cycles. Some of the cheaper ones the threads aren't all that great, and that could be an issue, too.

Same with mine. I hear ticking from the sink when running really hot or cold water. I think it loosens with thermal expansion and contraction