My "D"P and I have been together for five years ish, and moved into my old flat together last autumn ahead of a move overseas next year. We have very different waking/sleeping times due to our work schedules, so we have separate bedrooms for weeknights (then at weekends we'll often sleep in "my" bedroom ifyswim). As a result, the move-in meant that I relinquished my private office in the flat and turned it into his bedroom - I arranged for (and paid for - he's on a low income) delivery of a full new suite of bedroom furniture, new mattress etc. to turn my former office into his bedroom.
I realised a couple of weeks ago that DP has been sleeping on this now-6-months-old mattress without any sheets on - I'd never really twigged before, but when I started to look closely at it, it was absolutely disgusting. Filthily grubby, covered in bobbles where his pajamas had obviously rubbed against it. We had words (apart from it being truly vile, in my eyes, I've now got no chance of recouping any of the costs I paid for it by selling it on second hand) and he promised to use a sheet going forward. We have a laundry cupboard full of bedlinen, but I bought another new sheet so he could feel it was "his" to use in the future.
I've just stepped into his room because he was having a coughing fit and... no sheet. I'm furious.
So, Mumsnet...
AIBU to dictate DP's bedlinen use when it's not really hurting anyone?
Yes - let the poor man sleep however he wants!
No - protect the mattress at all costs!