If you had a larger roster, I could see potentially going to six starters, if you had six arms worth it. However, with only 25 guys (13 regular players and 12 pitchers), that puts a ton of pressure on your bullpen, since there would only be six arms out there. You could also end up with guys who go a week or longer without pitching, and that's too infrequently.
I want my $2.
Obligatory 2015 attendance record: 1-0 (6-5 in 11 over Seattle on 8/30)
If you don't know where you're going, any road will take you there.