Man, I feel silly now. I have several times more than $15K saved up. At grad-school living expenses, perhaps 3 years of runway.
I'm not really sticking with the day job for financial reasons though. I want to see the product I've been working on ship. Get it into the hands of actual paying customers. Because I figure then I'll get to see a whole bunch of other problems that will likely impact the startup too. Much better to make the initial mistakes on someone else's dime.
Problem is, my day job seems to move at a glacial pace. So despite having a 6 month handicap and about 1/5 the number of man-hours available, my startup may launch first. If that happens, I'll probably quit the day job whether it's done or not, because it's just a drag on the startup.