My BF and I have been together for 2 months and on the first two dates he did the paying, and I would offer to do the tip or pay my half. The third date, I treated him and then a few times after that I would always offer to pay my portion. Finally he said something like, "would you rather split the cost or just take turns from now on?" I opted to take turns and that is what we have been doing, for the most part. Although, if we are doing something casual like drinks at a bar or a movie, he always reaches for his wallet first.