if i was going all out to win, yeah i would try to fill in people on off days. who wouldn't do that? the benefit in counting stats vastly outweighs a possible slight BA hit. if you have the flexibility, why not do it.
the thing is though, if the league you're playing in isn't really hardcore, starting the season off by doing this, might not be in your best interest.
kind of like the reasoning in poker, that if you're playing at a weak table and people are just having fun, you don't want to sit there thinking over every decisions as it will just serve to elevate the play of your opponents.