So dripton has a very interesting approach to the Bless spell.
As you can see in this summary, they treat it as an ongoing spell.
So, you have put a Bless spell on each of your five companions? That's a -5 to cast additional spells. That's a big penalty to eat up, especially since Bless isn't something you can casually cancel. You're taking a solid, lasting hit for keeping your friends protected.
I'm still not sure I'd use the spell - my experience with it has led me to ban it in my current game - but it does make it a lot harder to abuse!