Almost all the time, I’ve slept in quite cold weather, seldom in winter, but cold due to the altitude or season, or both. And in a tent. Upstairs, there is usually a puffy synthetic sweater, as well as pants if it’s really cold, plus a clean pair of sox and oversox if feet are cold. So layering, but no sweating. In the unlikely event that sweating occurs, the whole bottom of the bag is unzipped from the feet up to the chest. When it gets colder in the wee hours, it is quick to just zip it up.
From threads on WPB rain gear, learned I’ve got a low metabolism, and the above does not apply to many people. But for some, the need to wash the bag is so seldom that I would pay Rainy Pass or the like to wash it professionally. Guess this hasn’t happened because new and better sleepwear has come out and the old bags were discarded, not because they were dirty or smelly, just because the material or zippers had worn out.
Limiting the bag weight and adding puffies also used in camp when necessary helps to keep the sleepwear weight to the minimum.
But am sure most of this thread does indeed apply to many with higher metabolisms, and the advice is good for those folks. Just don’t spread the “guilt” around to where it does not apply. Thanks.