ExpiryDate on a site cannot be removed
If a portal has an Expiry date set you can only change it but not remove it completely.
go to admin -> site settings
on advanced settings -> host settings
set a date for expiry date
now try to remove the date and you'll how this is not possible.
You should we able to clear the expiry date.
QA Test Plan
Verified fixed in 7.3.3 build 95
IMHO this whole feature needs to be dumped. It affects performance of all websites for the sake of may be 10 of 100k installations