[tbob]

I only make an offer to end early if it is a tough and needed card I rarely find for a set. My purpose is to pre-empt anyone else buying it outright. If a seller tells me that the auction will run to the end, I email him back my thanks and that I will be bidding, which I always do. I have just done this a few times and usually the seller will put a BIN on the card for my bid.
I used to be in the camp that would never ask a seller to end early but that was before I watched it happen for others again and again.
Again, only on a much needed tough to find card for a set and only if there are no other bids already on the card.