I've never seen one I've watched there ever drop, even though dates sometimes show 2 or more years expired. Not sure if it's a database date problem or they just keep them.
I had been tracking about five good domains with them, but they would never drop, even many months after they expired. I gave up out of frustration. I think that SignatureDomains.com hoards much more than NetSol.
SignatureDomains seems to have 3 big customers ???@ny?????.com, ???@ur????.com and ???@ea???????.net. Their names do not get deleted after expiring for 3-4 months and will be finally renewed.