I do not work for an organization which feels a need for LTS or any equivalent, so I don't have concrete figures to offer.

If I wanted to implement LTS or equivalent, I'd seriously think about having an automated install and test which you can kick off and leave. If it works, it works. If it doesn't, throw that machine out. Either way, very little human time is spent per machine.

Again, I haven't needed to do this, so I cannot offer direct experience about how well it does or doesn't work.

Cheers,
Ben