Nobody means to be rude when then ask "where do you find the time?" or they say "you have too much time on your hands!".
I understand they mean "wow, that must have taken a long time". I do find it strange that people can spend an entire weekend watching television (sports, dramas, reality shows) and nobody asks or says the same thing.
It's almost as if our culture has begun to look down on the concept of putting forth effort. You can waste as much time as you want on any number of endeavors, but if it results in a tangible 'thing' it somehow moves into the realm of needing to be evaluated in terms of how much time you spent on it.