Is it rude to take all the time allowed to make an offer decision? I've been made an offer for a position that I will likely accept. I've been given a week more time than planned (at my request) to make a decision, which makes it possible to attend a campus interview (already scheduled) for another position, although it probably won't be as good as the already-offered one.

Knowing this, should I just accept offer A? I feel bad taking the full extended time to make a decision that I've pretty much already made privately, although I feel that I can't cancel the campus interview since they already booked the travel accommodations (on the same day I received offer A no less). (And I suppose it could actually be a better offer).

Will it hurt me to take all the time they've given me? I would literally be letting them know maybe 1 or 2 days ahead of the full bracket. I don't want to look like I'm dragging my feet and they've made it clear that they're trying to close it out quickly. My assumption is that they've given me time, so I should use it- but I just don't want to hurt my chances. 

The alternative however would be, I suppose, to accept offer A and then attend the campus interview, which sounds worse. Thoughts? Thanks.
Not at all. You should go to the interview, see the competing offer, if you get it, and then decide. Note that you will likely not have time to have either school make a counter offer. Therefore, I would recommend that at the interview you let the school know you have an existing offer and deadline and that they will have to move quickly and at least match the other offer (or whatever it will take to get you there).

If the school that has made the offer asks, just tell them you are waiting to hear from one last place. You could send a preemptive email telling them that, but there really is no need.