I layer in the summer, layer in the winter - doesn't matter, I like options (one of which is sleeping alone* no matter how much I love Himself). In cold weather I have flannel sheets bottom and top, followed by my winter weight blanket, followed by my medium weight down comforter in its own duvet cover. In the deep cold I even have a cotton or fleece throw across the foot of the bed that will come as high as my waist in case my lower body is chilled. When I can see spring in the offing, I swap out the winter blanket for my summer one and the bottom flannel sheet for a cotton one. A little warmer? Off goes the comforter/duvet and on goes two summer comforters. Why two? Because when I got to bed I like it warm, but as the sun warms the front of the house the bedroom gets warmer - so I toss off the top comforter to the floor and slip right back to sleep. When it's warm weather I have top and bottom cotton sheets, summer blanket, and the lighter weight summer comforter tops things alone. As autumn approaches, I reverse that order.
*We were both restless sleepers. From early in our marriage (1974), I would wake in the middle of the night, grab my pillow and alarm, and head for the guest bedroom (or couch, when we lived in apartments) a couple times a month. We continued this pattern for decades. Them Himself developed a back problem in 2000. He moved from bed to guest bed to couch cushions on the floor, to recliner - the poor guy never slept in the same place twice for a miserable six weeks until his surgery. Meanwhile, I slept somewhere else because any movement by me made him hurt more. Some of the best sleep I had in a while. After surgery we were back to one bed...and I was back to wandering to another one a couple times a week. Separate beds during his recovery from cracked ribs and a broken collarbone (motorcycle accident #1) and recovery from a broken thumb and the other collarbone broken (cycle accident #2 - and then the bike came off the insurance

) When we realized that we each got a better night sleep in separate rooms the nightly question became "do you want to go to bed, or do you want to go to sleep?

It appears that we may have been at the forefront of a trend - just google "sleep divorce". As many as 1/3 married couples are happily married and even happier sleeping apart. Who knew!