I usually do what I'm told, but a couple of years ago, I managed to
talk SWMBO into swapping out our two 30 degree sleeping bags for two
zip together summer weight fleece sleeping bags that we augment with
an assortment of fleece blankets.  Added or subtracted as needed.
That arrangement works very well for three seasons.

  We sleep in the loft with the addition of some cheap ass memory foam
that I bought at Big Lots and placed underneath the mattress.  I cut
the foam into two sections, one for each pad so it doesn't affect
folding the bed and closing the top.  Two inches thick, if that, but
works amazingly well, if it weren't for that little extra padding, my
bony hips couldn't tolerate sleeping up top there.

  Sheet thread count is zed, none, goose egg.  We leave the good stuff
at home and don't bother with sheets.

George/ATL