help with some numbers

I'm looking for an idea of the average time needed to
complete a game of eight ball versus one pocket. I'm on the
committee that oversees the activities of a fraternal
organization. We have a nice nine foot pool table which the
members can play on at no charge. Apparently someone
recently complained about the fact that there are no house
rules, as I'm one of the more frequent players I was asked
to come up with a set of house rules. One of my pet peeves
is that we have a couple old farts who like to shoot one
pocket. I have no problem with this as long as you don't
have people waiting on the table. One of the rules I was
going to post is you can play any game you want as long as
you don't have other people signing up to shoot the winner.
Once you have people waiting, the house game reverts to
eight ball. The skill level of most players who tend to use
the table frequently is between a C+ and a B- Of course I'm
basing this on the fact that I believe a game of one pocket
lasts significantly longer than a game of eight ball but I
have no evidence to support this. Thanks in advance for any
insight on this.