There's some lenses that have "locks" sorta... I have an Oly 65-200 that has a macro twist+click in it's compressed state, which holds the lens together, and with some AFs the lens stays put. Still, the earlier optics are heavy and excessive looseness is just an age problem probably. I wonder if there's a marginally invasive method to "rejuvenize" the felt ring inside, like maybe carefully using something safe... like what fabric softener does to synthetics... assuming that the felt is synthetic. My understanding of lens components is that they are "dry" in their parts movements, and any lubricant is minimal in manufacturing, if at all.