Always plan to start a new world, any previously explored areas wont be updated with any updates and you could be missing something because you explored too much already.

I like building a lot and plan on making a huge build that takes a long time but I will delete it all in a hearbeat for an update to start again.

I play on Valheim seed for eg and after a few updates idk which one exactly but one of the updates added one of those stone circle points of interest right at the place where I always plan to build my base and it is a great addition to the area I want to build in.

Also if terrain generation algorithm is changed in any way for whatever reason in an update new unexplored areas may not match up with previously explored areas, I dont think they ever have done that and its always been safe in that regard to keep playing on old worlds but it can happen depending on what they update.