As I have gotten older, I am evidently sleeping cooler, even at home. What seems odd to me is that my legs are the parts that get cold, so most of the time I now have to sleep with long johns on. Issue army polyester ones (don't like the tops, though) work for me when it is cold. But I wear those only when it is cold enough.
I have experimented with other ways of sleeping without a regular sleeping bag but they never really worked. Among other things, the sleeping bag provides a very soft and cozy place and a degree of padding that you don't get with a wool blanket but the wool blanket is much better for me in warm weather. At this point I want to edit the above to explain my experiment. I read somewhere in an old book that the sleeping rig of certain exporers consisted on their regular clothing with something wrapped around their legs, more or less from their waist to their knees. It didn't work for me because, for one thing, the clothing necessary to keep my top warm (jacket, coat, whatever) was unnecessary during the daytime, since there was and usually is a big difference in daytime and nighttime temperatures, coupled with the high heat producing activity that walking with a pack usually is. I didn't get cold but I didn't gain anything over a more conventional system.
I have never tried using a liner, which would probably be a good idea if you used your sleeping bag frequently. We have had ours for over 25 years and they have never been cleaned.