Maybe I'm the odd one out but I'm no rush to defeat bosses. Almost 500 days in and I have face Yagluth, let alone find him.😂
I also visit my some of my earlier bases less often and when I do I'm greeted with darkness, with all my light sources depleted. So the coziness I had so lovingly established is gone, until I refuel the light sources and fires around the place.
A simple suggestion is to increase the duration of light and fire sources as you defeat each boss, hopefully to a point where the don't need refuelling.
I'm thinking more towards your bigger bases where light sources may be scattered over a large area, or even in places that may prove hard to reach. Additionally, it's always nice to come back to a place after a while and be greeted with a welcoming glow of warmth and light.
Wouldn't it be a nice QoL to achieve almost permanent light and fire sources as you progress in the game?
Source: https://www.reddit.com/r/valheim/comments/n6c3p4/suggestiondefeating_bosses_unlocks_norecharge/