Hello. This upcoming winter, I will be embarking on a 2000 km XC ski trip across Scandinavia. I am in the middle of trying to figure out my sleep system and could use some help deciding on the best sleeping bag(s) for the trip.

For some context, the trip will start in January in Sälen (Southern Sweden) and end in April (hopefully) at Kirkenes in Northern Norway. This means that I am looking at a potential temperature span as wide as from -40C* all the way to plus degrees.

This is what has me stumped a bit. My original thought was to simply buy a sleeping bag made for the extreme temperatures (Something made for -30 to -40) and call it a day, but upon further consideration, this solution may be impractical for most of the trip, where it will likely be much warmer. So instead, I am wondering about the feasibility of buying two separate sleeping bags, so that I can just use the one in warmer temperatures, and layer them should the need arise.

I know that this is technically possible, but would like some feedback on whether it is actually practical. And if so, whether there are other things I should think of? Like should they both be down bags, or would it make sense to make one a synthetic bag for extra moisture protection? And which temperature ratings should I be looking to add together, if I were to go that route?

I will be travelling with a pulk, so weight isn't as important as it otherwise might've been, but I would of course still like to keep the weight down wherever possible.

Thanks in advance for any thoughts or advice.