I agree with this too. Who is available and then even where in the lineup the opponent is plays into it for me. If whoever I bring in gets out of the bases loaded jam unscathed but the top or heart of the order would then likely be due up in the 9th, the decision of who to bring is will be different than if it's the bottom of the order we're talking about. These decisions aren't made in a vacuum. I still have to play out the rest of the game.
At some point, the other arms in the bullpen have to step up. It doesn't matter when they pitch. There's more guys in the pen that I want nowhere near a high leverage, late game situation than I trust in them.