I struggle with this all the time. I have 2 setups one summer and one winter. And of course I have been unhappy with both. I was in the south last week with weather forecasts at night in the 40's, so I brought summer gear. Well, they were wrong and it was in the 20's. We had a down throw and that kept us ok, but not great. I've also been to Glacier NP during a heat spell and had our winter setup. It was horrible. on with the bag, off with the bag, we were both sweaty messes and I'm sure our winter bag sucked up our stench. So I would say buy for the season you use the most and get some sort of liner to extend. But if you really need cold weather gear, you should just suck it up.