If you're talking about additional installations with those keys - they won't activate after you stop paying.
Regarding already installed/activated software, it's going to depend on which subscription you're on. I don't pretend to know all the permutations, but I know that our Gold Partner MSDN licenses are good only so long as we continue paying annual subscription fees. If we stop paying, we're to immediately uninstall everything.
Other programs, in contrast, allow you to use what you have installed for as long as you like, though you can't register additional copies, nor download from MSDN after the expiration date.
Call up your MSDN support number and ask. I've asked numerous licensing questions without triggering any audits. ;)