I often work odd hours and so have become familiar with the custodians everywhere I’ve been (more familiar, sad to say, than with many of my colleagues). But I haven’t (yet!) been employed by enough schools that I would have any standing for sweeping generalisations. Somewhere, right, there must be college custodians who don’t just put the recycling in with all the rest of the rubbish? Even when you are not watching them?
(I’ve never complained to the custodians, their superiors, or anyone else about this. I’ve a strict rule against doing anything to anger alienated labor when it has unrestricted access to my things.)