Some of the Bonvoy levels do have a "lifetime" status, which depends upon the number of years you have had at least that status plus the number of nights you stayed. Platinum, Silver, and Gold all can be obtained this way, and your ownership nights/years also count towards this (there are some Titanium lifetime members - but this was obtained when they merger the SPG and Marriott programs).
For instance, with about five more years and 140 nights I should hit Platinum for life - so even if I sold off all of my Vistana ownerships at that point, I would still retain that status for the remainder of my life (I'm currently titanium based on stays though). We should get Platinum status with our 3* ownership as well, so once I get platinum for life we will likely switch so that my spouse becomes the primary on our Vistana ownership and we would both be Platinum.
Personally, I have not noticed much difference between platinum and titanium, upgrades are few and far between, and you feel like you have to beg for a free breakfast. The only real difference is more bonus points. It would not be enough to make me buy TS points just to get to the 4* elite/Presidential level.