One thing to consider is that if you leave the nail inside the bone, it could cause severe tissue damage if you had an accident that caused the tibia to break. You also don't feel quite right while the nail and screws are still in place. I had the 13mm BetzBone in my femurs for 1.5 years after consolidation, and I could always feel, it espcially when jogging. Tibia would probably be different but the sensation remains as long as the nail is in. Remember also that the nail occupies space that would otherwise be used to store yellow bone marrow which serves an important function in the body.
If you are considering external fixation, I would advice that you visit a doc that does the procedure and ask to see some of the patients who have completed lengthenining or at least see pics of their legs. The scars are hideous! When I was getting my femur nails removed, there was a guy doing a consultation to lengthen his femur. He had done external fixation on his tibias and while he was happy with the height gain, the scars basically made him never to want to show his lower legs in public. External is cheaper for sure, but there is a price to be paid for the rest of your life due to the scars.