Not that I'm in labour yet but due a week on Saturday so not very long to go ...
A little background info to help you decide:
dd1 - 16 hours from start to finish - had an epidural which they reckon slowed it down.
dd2 - 8 hours and ditto the epidural
ds - 4 hours (waterbirth, no intervention)
Soooo ... m/wives seem sure it could all be over in 2 hours, I'm not so convinced myself!