I had a lifetime warranty on an alternator, I used that warranty many times over ~15 years.
The last time it failed the retailer claimed to have no record of me ever having bought an alternator from them.
I bought a new Alternator from Autozone( different retailer) , a different design alternato with internal fans, but the same 50/120 amp rating.
Arrived to door in less than 24 hours. Made in malaysia. It does not make its rating, about 32 amps hot idle and 109 amps max. but off idle upto its max the power band is pretty good.
I took apart my failed 'lifetime warranty' unit. Pretty easy to access rectifiers and brushes via tailcap. The brushes were not aligned with slip rings, with the lower brush bridging the gap. I lowered brush holder and thickened the parallel AC straps with fatter copper, and sanded flat the rectifier plates and the casing where they attach for better thermal transfer, and removed the New AZ unit and returned the non lifetime warranty unit.
Looks like they missed, badly. Surprisingly it worked fine for 4.5 years like this~25k miles, and often, it was told by my adjustable voltage regulator, to make everything possible towards its 120 amp rating, feeding a large depleted low resistance AGM battery, over a thick copper circuit.
bobistheoilguy.com
When the alternator failed I was 20 minutes into a 2:15 hour drive at night. I knew I had enough healthy battery capacity to get there, but kept a close eye on my digital voltmeter, and arrived with 12.23v or so. Expecting to see 14.7v and seeing 12.7 alerted me to the issue. I also have a digital ammeter showing amperage into and out of the battery. I was up around 25 amps of load, which is how a battery's reserve capacity minutes are measured. I turned off stereo and blower motor for about 20 amps of load. Also had a jumper pack for 18 additional amp hours of capacity, but it was not required.
Good luck on your next reman, as it is luck of the draw.