Something else that has not been brought up yet, no matter how great the cobbler, they just cannot rejuvenate worn out boots.
If you indeed have a couple of thousand miles on them, well, that's about 1500 miles too many.
Good boots can "last" a lifetime, and as everybody knows, nothing beats a comfortable pair of shoes. But when hiking tough terrain and often with very heavy loads on your back you are doing your feet, and the rest of yourself harm by hiking in worn out boots.
Do your body a favor and go get some new boots.