You don't want to know how much email I have archived from before gmail (it goes back to 1993... some of it is in pine). At various times I've transferred the archive into newer formats so I can still access it (at the moment all my archives live in Mail on the mac) but it is a giant pain to search.

I occasionally transfer some of the old mail into gmail for easier access, but honestly I don't want my gmail burdened with every #$%@! message I've ever saved.