I have two, five years apart. They get along terrific, but that's not always the case with that kind of spacing.
I have a sister, 2 1/2 years older, and I was 12 when my little sister was born. I've found that (in general) the wider the spacing, the better they get along, possibly because there isn't as much rivalry between children from disparate age groups. But ultimately, kids either get along or they don't; depends on their personality.
We thought about how long we want to have dependants in the house, according to when we want to retire. As for me, I just need more time to heal between babies, but everyone's priorities are different.
Use the spacing that fits into your life best in the long term.