My friends blow their lines. The dealer I bought our last TT from only blows the lines if doing a winterize service. I only blow. Only dump antifreeze down the toilet and P traps. I live in Oregon up I-5 north. Temps are pretty moderate in the winter. Only get freezing on occasion and day time temps are above freezing. If I lived where it was freeing for days on end I think I might do the antifreeze.
I like the fact that come springtime I just fill with water and it's good to go. Just gotta get the air out of the lines. No draining antifreeze.