Never hurts. Could be a good opportunity to look around the threadiverse and see if you find anything interesting.
However, as it only affects the domain, I expect the Lemmy developers will manage to migrate user data to the new domain should lemmy.ml go down. So your account won't just disappear, but it might go down for a while. It might also affect communities hosted on .ml domains, as followers from other instances will not have the correct path any more.