This is a personal question isn't it>? - but it makes sense to ask as I was asking exactly the same time as you. We started trying at 9 months because we wanted to have children before we got too much older (i am 29 and DH is 33) - THis may not seem old but I look at DH's parents now and they are extremely old grandparents whilst mine seem to be years younger (they are but my grandparents seem younger than DH's parents = IYKWIM?)
We had to consider age, work, money etc etc etc.
Good luck