building ghc once or twice?

I have been packaging ghc for a long time... In older times I think it was recommended to first do a (quick) build of a new version of ghc (with the previous version) and then to do a (perf) rebuild of the new version against itself. In fact I am still building ghc this way for Fedora: though it seems like this is overhead nowadays...? (I think one major reason was to get stable ABI hashes for the core library packages.) These days should I just do a single default or perf build of a new ghc version against a previous stable release, or does it still make sense to continue to build in two steps like I have been doing? Any pros or cons? Jens