Home I keep pretty clean, I probably only have 50 emails...
Work

different story, I have in my inbox and PST just short of 2000. Most of it is read, but I'm in an org where everybody emails the entire distribution so a lot of it I just glance over for the idea of what's going on, or ignore it entirely

On occasion I just go through and mass delete stuff to clean out the inbox
I've seen some people

GIGS of PST's (Mail files for Outlook)
Some people just don't delete anything.