For Precise (Dr. Paley, Dr Rozburch, Dr Pili) and Fitbone (Dr Monegal, Dr Baumgart) which are partial weightbearing you need to wait for 2-3 months on a wheelchair then 4 additional months in crutches until being able to walk without support. However I know Dr Monegal prefers lengthening in 2 steps, first one leg then the other. In that case, his patients could tell you the details. But I believe you walk with crutches earlier that way.
For Guichet Nail (Dr Guichet) and Betzbone (Dr. Betz), I know only the first, and in my case I used crutches immediately after surgery for 2 months and then started walking without support (even before stopping lengthening).
If you do external (Russian doctors, Dr Catagni), then you can opt for LON or LATN which limit your amount of time with frames however there is a real issue about permanent knee pain. There are some external devices which allow you to walk after lengthening (weightbearing). Again I don't know detail about these, I think TSF?