Seller delaying offer response and collecting other offers--what would you do?

[Mike Day]

I've put an offer on a small apartment building that was supposed to expire in three days. The seller has said they need additional time to deal with a lien and are expecting to accept my offer and start escrow any day, however in the meantime they've been collecting other offers. A week ago when I sent my offer in, there was only one other offer, and mine was the best, but now I've been told they are up to seven. How long until they collect one that's better than mine while keeping me on the hook? I'm more than tempted to withdraw my offer but my agent is vehemently against it. Any words of advice?