depends on how large your base was. you can bring the materials over into a new seed with some extra effort but the shaped ground and good base spot is lost of course.

it also depends on how much of your current old seed you had explored. if it was only like 25% you can keep going with it probaly.

if you explored like 80% of the map definitly start fresh.

i read from older posts that mistland generation is much better with a fresh seed. which is sad given that will mean Rip for my current seed when it comes out. oh well. atleast i can keep all the 1000s of marble and just bring em over and rebuild with it once i find a decent spot near the ocean in a plains again....