How long until we reincarnate?

It's a big puzzle if you want to plan your next life while you are on the Other Side. Especially when you do it consciously with many layers in your existence on Earth. You've got to organize a gathering with your friends and weave threads for the next life, wait for everybody to be present on the Other Side. It's a huge organizing. I've had many dreams around this subject. Very interesting, although I understand in my dream, once I am awake I am a bit confused. In my dreams, we don't do all the work ourselves. You can use general patterns and fill it in with your desires.
You can also just jump in, without much planning. I think you can compare it with a fast-food meal, or a meal from a three-star restaurant. Whatever your taste.
So, when you just jump in, you can return as fast as possible. If you want to wait for your dear friends and family to join you next time, you need more Earth years, and according to plan. So for example, if I want to be Graham76man's daughter next time (I use you as an example because your last post is above this one) we both have to die first, and I've got to wait until he/she (you can be either sex next time) is old enough and has found the right partner to make children. It takes earthly years.
I also think everybody comes for different purposes, different interests.
I also think there is another reason why the populations grow: we live in interesting times. In the past, situations in countries were the same for centuries, and nowadays change goes quick.