It doesn’t happen often, but sometimes I do give up on a puzzle. A couple of times I’ve put it away to try again later, but in most cases, it’s definitely goodbye. Here are two examples:
I just couldn’t get the edges and the last bit of grey right. I tried many times, but in the end, it was no fun anymore, so back in the box it went. It’s really too bad, because I love Escher’s stuff, but all Escher puzzles that I’ve ever seen are horrible quality. Selegiochi is an Italian manufacturer, and I’m obviously not getting any more of their puzzles (I don’t know if they’re even active in the puzzle department anymore). It wasn’t cheap either. At least one person managed to finish this, though, since there’s a photo on the Jigsaw Wiki. I take my hat off to whoever completed it.
A more recent case, a puzzle I bought at a flea market. Arrow puzzles (UK manufacturer) are generally not good quality, but this was especially bad. You can see how the pieces wouldn’t stay flat. Again, I just couldn’t get the final bit of sky together. I took some of it apart and tried again, but pretty soon gave up.
When it’s no fun anymore is when you should give up. When there are so many enjoyable puzzles available, why do something you don’t enjoy?