I recommend moving to a new server when it’s time to upgrade as an in-place OS upgrade requires lots of downtime and might have issues. So I mostly don’t move folks to a new server until the 2nd LTS release (i.e., I’ve sites on 22.04 that I’ll upgrade this year, likely waiting until 26.04.1 gets released in the summer.
Moving to a clean install requires zero downtime (especially if you can do it with a static ip that gets moved to the new server once it’s writing) working).