One reads more often than not that
and most sources seem to explain mechanisms of LTP that just last as long - from hours to days to weeks to months. Only rarely it is explicitly mentioned that such-and-such LTP lasts for years or a lifetime, and most authors seem to hesitate to make such claims.
But there are memories (and learned skills) that can be retrieved many years and even decades later, even though not (consciously) used in the meantime.
I have no idea how this kind of "really long-term potentiation" is explained. Three options come to my mind:
The long-term potentiated synapses and the "memories" related to them have actually been used in the meantime (just "unconsciously" or in completely different contexts) and thus been re-newed and re-strenghtened every now and then.
They degraded but have been re-newed without having been used, but by some other mechanisms than "normal" LTP.
They actually did last for such a long time (i.e. didn't degrade) - and the authors just hesitated to claim it (because they could not prove directly).
Is one of these three explanations the correct one, or is there another one?