For anyone who has moved name severs for a domain name, what is the longest you ever saw it take?

I have a customer who (against my will) signed up for yahoo webhosting. They wanted me to move their site from the existing host to the new host. It really only involved changing the name servers at network solutions to point to yahoo, and upload the site via FTP.

Well that was Sunday morning, and now its Tuesday morning, and still no site.

Network solutions changed the name servers properly and it is pointing to yahoo now, just no site, and yahoo said they can't help me until the site has been down for 72 hours. Then they will look at it, which is total BS. I have never seen a .COM web address within the US take more than a few hours to propagate, they are telling me it takes a full 72 hours for this to happen, which even network solutions said is crap.

So what is the longest you ever saw this wait take?