Just wondering about this myself. DS is 24 months and he's going to spend about 24 hours at his dad's house, from this evening to tomorrow evening (deep organizing time and maybe even a night out on the town for mama!). He doesn't nurse a ton anymore, maybe three or four times per day, and he easily goes 8 or 9 hours without nursing at daycare. He's done overnights at his dad's house with no problem, but I've always picked him up pretty promptly the next morning and nursed right away.
I think he'll be fine without nursing for 24 hours and just drinking cow's milk, but I'll probably have to pump a little for my own comfort. I think I'll just pull out the manual pump and take a little off the top.
I don't think either of us are quite ready to wean yet. The nursing relationship is winding down, but it's still a pretty important source of comfort and nutritional insurance, especially when he's sick. He's also had three ear infections recently and I want to keep up that immune system boost.