I'm not sure what you were reading, or if I'm interpreting the question correctly (saw similar mention in Sub-Forum post) or not.

With gabapentin & Lyrica, there are maximum dosages beyond which increasing dosage further adds no further benefit. IOW, they top out, so there's no point in increasing dosage beyond that point. Some people can use these medications for many years without ever reaching those levels; others can reach them within a few years (or less?) Everyone is different with many different causes/types of PN/neuropathic pain.

Gabapentin/Lyrica sometimes do stop working for some people.

In either case above, they try switching to Lyrica, Topamax, or something else. There are many medications being used, and more in the pipeline.
Google: medications for peripheral neuropathy

Doc