We left when we did as we had a window between the time my son finished school, and the time my youngest daughter started.
Why? lot of small reasons adding up, I hadn't been able to take leave for four years, my wife was being pushed to accept promotion she didn't want, we wanted to slow down and take control of our lives. We had had two years where the weather had been so lousy in the afternoons after work we hardly used the pool, I wanted a lawn that didn't grow as quickly as the kikuyu, so if I didn't mow it one week it didn't need a tractor the next week. My car was going to need new tyres in 6 months, the fridge and microwave were going to need to be replaced within a year, so it all added up to being a good time to have a change.
I suppose we didn't really have a single compelling reason, should we have had???