Unfortunately, it seems that modern "dumb" (or feature) phones now are being required (or only) to support LTE and their stand-by battery life has declined quit

Unfortunately, it seems that modern "dumb" (or feature) phones now are being required (or only) to support LTE and their stand-by battery life has declined quite dramatically. Many now seem to advertise battery life of quite a bit less than a week. It's unclear to me why LTE appears to consume much more power to "do nothing." But I recall easily getting a week or so of actual battery life being completely normal a decade ago.