In my mind, age differences needn't matter. What matters more is how two people interact.

I'm a bit uncertain about the how long to wait question. If you feel comfortable, could you elaborate more? I don't find myself able to answer, because it could be a question sparked by a couple different scenarios needing different answers based on what's driving the question.

I've had and currently have a twelve year span. My maternal grandparents were about 8-9 years apart, and my paternal grandmother was a year older than my paternal grandfather, which back then raised eyebrows. Eyebrows not much raised with maternal grandparents.