How long does pancake batter last in the fridge?
Bisquick-originated pancake and waffle batter lasts a day, two at the most. 

Data: in college, I made pancakes or waffles every day for a year and a half, making the batter on day 1 and then cooking it on days 1, 2, and 3. Once in that time I got sick on Day 3. Based on that experience, more than 24 hours is getting sketchy, though 48 seems to work most of the time.