Last Days shouldn’t reasonably last hundreds of years.
Exactly!
While I agree with TD's stance on 1935 (it's a "plot hole" than has not, and probably cannot, be squared), I think this is a far bigger issue for the WTS.
When it comes to anything remotely complex, most JWs just shrug their shoulders & say, in effect, "well, I don't get it, but surely these guys 'anointed with holy spirit' must have figured it out, so if they say it is so, it is so."
But "the last days" is not hard to fathom. Even the most mentally challenged JWs understand that "last days" must mean a relatively short period of time.
Per current JW doctrine, we've been living in "the last days" for 107 years now. There's maybe a few hundred people on earth who were alive then, but no one would be able to recount clearly their own personal memories from 1914. 1914 is completely, entirely, absolutely a "history book" date - no one alive can recount their own "1914 experiences".
As time moves on - and JWs claim that the "last days" have lasted 120, 130, 150 years - what little credibility the "last days began in 1914" doctrine has left with wither and die. The sense of urgency for preaching will completely evaporate
TL;DR - Jesus & Paul talked about the "last days", not "the last centuries". If the "last days" can last more than one century, why not 2, 3, or 15 centuries?