I recommend just start budgeting a certain amount every income period, and just stow some money away year round.
I have a friend and colleague, a Brooks Institute educated photographer, who says that a man is entitled to a couple of vices. Some men, he says, smoke expensive cigars and some men drink expensive single malt scotch. If you don't, you're entitled to put that much money away for hunting and fishing. It might add up to quite a bit. We both had studio space in the same building and I would have the occasional bamboo fly rod or pair of Gokey boots shipped to the office because I didn't want them delivered to our front porch with no one home. We also would have Christmas parties together. One year after the Christmas party, my wife and I were driving home and she said, "Jack says you smoke a bit. What does he mean by that?"
