It is possible the lipoic acid is enabling mitochrondrial functions.

This supplement is combined with acetyl carnitine for that purpose in the product Juvenon.

So if that is true for you...and this is only a guess, you may need it daily from this day forward, as your own system is flawed for some reason. (aging is often pointed to for mito decay). Lipoic acid is a natural substance our bodies make, and may decline with age.
http://www.ncbi.nlm.nih.gov/pubmed/15919137

I would continue with what works for you. After a year on the lipoic, you might try stopping it to see what happens.

Do you know for sure you have nerve damage... and not just aging mitochondria? These factors are relatively new, and there would have to be more research in the future to clarify things.

I wouldn't add amitriptyline unless you really need it. Since the lipoic works, you seem okay with that so far.