All I am going to suggest is that you go with your gut. Do what feels right. I always thought I'd have a bigger gap than we do, but I changed my mind after a family holiday last year. We used to do big camping trips and DH lives for these. I decided that I was unhappy taking children under 3 years old on these trips, so we decided to have our kids closer together so that we could start taking the holidays again.
I wish I hadn't made that decision. I love my girls, but am finding having them this close together really difficult. I wish we had've waited until they were 4 years apart.