Its really up to you when you choose to move on. I think I rushed Eikthyr today personally on day 11/12 but I did it to get into bronze. My last world I played up to the Elder and had almost everything fully upgraded and was dipping my toes into the swamp before I went to take him on. then life caught up and I didn't go beat him up. I had a lot of fun just building and planning out my base though up to that point and had been working on a secondary location by the swamp.

I find Valheim to be very much 'at your own pace' when I rather enjoy. There are plenty of people who put dozens of hours into the game before they even touch the bosses.