It's a hard call........being "picky" is really quite subjective - but in the end, you have to be able to understand that there's a point where YOU have to believe that enough is enough. Perfection is relative - what you may think is ordinary, others may think is simply fantastic.
You also have to determine just what it is you're trying to accomplish.......are you building for a contest, for a client, to try to make the best model you've ever made regardless of the effort required, or make a model as well as you can and still have fun?
For me, it's all very personal - and it also depends upon the subject matter - for some subjects I hold a particularly high degree of emotional attachment or passion - those models often get more attention (somewhat OCD type attention). Others tend to get a little less attention.
In the end, you just have to please yourself and have fun.