I don't know that there is a magical "right" time to have another baby. I think if you are ready for one then go for it. There will always be obstacles, there will always be second guesses about the timing, you will always be tired, you will always have to make adjustments, etc. And no matter whether your children are 2 years apart, 6 years apart or 18 years apart you will make it work.
My kids are 14 months apart. We didn't plan it that way and I absolutely didn't want kids so close together. I had a c-section with my second and the night before going to the hospital I cried for hours. I didn't want my first born (son) to ever think I had another child so quickly because I didn't love him enough. I didn't want my newborn (daughter) to miss out because I couldn't give her as much attention as I had given my son when he was an infant. I didn't know how I was going to get anything done with a toddler and an infant who both need a lot of attention and both take up a lot of space in the grocery cart. LOL! I didn't want to have two kids in diapers at the same time. But you know what? I now wouldn't have it any other way. They are so much fun to watch together. They play with the same toys (safe for 3 and under) and they also fight over those toys (sharing is a hard concept). They both have times when they crave attention and when they want to be independent. The diaper thing isn't such a big deal, though I will be glad when they are both potty trained. They truly bring us a lot of joy. If we had waited until my son was 2 1/2 or 3 to try to start having another baby we wouldn't have my daugher. My son was diagnosed with leukemia last fall. Not knowing how sick he would be, what the treatments would entail and how much time he might spend at the hospital, I would not have taken on the resposibility of another child. But we've adjusted to our "new" life and are doing well. I'm getting off track a bit, but am trying to show you that you can find a way to make things work. If you are ready to have another baby, go for it. Then follow your instincts, be open to change, be a creative problem solver, love your family and make it work.