With more than 1000 hours of play in Valheim, I can say the loss of rest bonus after exiting the game has been the #1 cause of frustration and problems for me. Want to log out in a dungeon because it's time for dinner? Too bad. You lost your rest bonus. Want to log out while exploring the plains and still have 20 minutes left on your rest bonus? Too bad. You lost your rest bonus. In the swamp looking for turnips and an important call comes that requires you to take off for a bit? Exit and lose your rest bonus. Note this is all in single player (non dedicated or hosted server mode).
And of course it's very easy to forget when you log in that it's gone.
I honestly have no idea why this issue exists within the game, and has since day one. Saving the rest bonus and allowing it to continue on a reload is just common sense. Why is Iron Gate not addressing this problem?
Source: https://www.reddit.com/r/valheim/comments/zwtnle/the_worst_feature_of_valheim_losing_rest_bonus_on/
