People who only have a goal of killing the bosses and nothing else beyond that will be bored in less than 150 hours depending on how many players are in the lobby and a lot of that depends on much time you take farming materials for food and armour and the seed you're playing on determines how much time you'll be looking for crypts or silver veins, when rushed I cleared the game (killing the 5 bosses) in 83 hours with silver gear on my 2nd solo play through, but some people have spent 300-1000 hours from building and making events with other players in servers or using mods. Valheim is amazing in many way depending on how you look at it, I guess it comes down to what you're looking for, me personally i enjoy building with groups and going on hunts, after burning myself out on vanilla i turned to mods. No harm in taking a break and coming back in a few months