I think it's ~5 days post surgery when lengthening begins with precise and Paley. If memory serves less for 20 yr olds and more for 40+ guys. Femurs are safer and faster recovery. Given you say only 3.5-3.8cm then likely you will manage without having to slow down for soft tissues, which means 1mm/day. I think technically they lengthen 2mm during surgery to be sure the nail is working properly. Might only be 5 days plus 35 days, for total 40 days. Everyone is different, no guarantees, but common is for consolidation to take as long as lengthening. Assume another 40 days for typical consolidation. If you work hard with exercises Paley PT will give you and the stretching, and use your walker a lot, and walk in the pool a lot, you'll minimize muscle loss. Given shorter timeframe you'll probably be able to recover fairly quickly. It's possible your walking normally 4 months post op if you're really only doing 3.8cm precise. It's also possible you grow bone slowly and Paley or Robbins have you slow down to 0.5-0.75mm per day, and it's possible a nail malfunctions and has to be replaced or something else goes wrong. If you're not a vegetarian, 4 months is realistic, if you work hard (note: most people say/think they do but don't actually). It could take till 5-6+ months post op for you to walk normally if you're not dedicated. During my LL, I met a Paley patient that could not walk normally ~1.5 years post op after 7-8cm LL. He noted being vegetarian was detrimental to his recovery, so consolidation took forever and hence muscles completely wasted away. It's also possible to lengthen 7.3cm and go hiking and ski black diamonds in CO ~7.25 months post op. Results vary a lot by patient, there are no guarantees. Good luck with your LL journey.