One week to negotiate an offer?

In a recent "In the Pipeline" thread, a surprising tidbit from a biotech hiring manager:

...More recently, I made an offer to a recent PhD grad. Again, it was a very generous package, yet when the offer was made, this person came back saying he was worth more (despite him not having any industry experience). I felt like pulling the offer right there. Instead, I waited him out, and when the one week expiry came, I told him we had to make an offer to someone else. I found out later that he was holding our offer to a competitor in order to get a higher salary from the competitor. Good riddance that he was never hired.

There are a lot of interesting details here, but the 1 week deadline on the offer seems a little short.

I am under the impression that two weeks is a reasonable time frame, but maybe I'm wrong. Readers, what has been your recent experience?