6-8 I think :P
Hmm...they used to have a Trivia game I won several trophies for playing but it took some dedicated typing. Several times I must have done 7-8 hours straight [excluding food/bathroom breaks]. Now the games are gone I average less than an hour a time but do it more than once daily.
11 hours...at least....
Probably about 6 hours when I type several experiences.