I personally think it is a individual thing..
I brought Zefra home (she was 3 months) when Stark was just over 2 years old. Stark was an "easy" dog to own, once we got his reactivity under control!
Zefra is a fun dog, tones of work in regards to her training schedule... lol.. my fault, not hers... lol... but again, a pretty easy dog to live with (for me).
I would like to add another dog and there are a few breedings I am looking at but nothing is set in stone.
Only YOU know what you can handle and what works for YOU.