I have my DHCP Lease renewal time set to 9999.
By my math that is about 6.9 days to lease renewal (ignoring the 50% of time thing in the RFC).
WEll, after a couple of weeks of it working just fine... renewing the leases after about 50% of that time (after about 3.47 days), the wireless on my router just
FROZE SOLID at about the time I'd have expected it to renew the leases, after 4 of these more or less twice a week renewal cycles. The fixed wire network links all still functioned fine.
As others have said, the router needs to be rebooted/power cycled for the wireless to work again.
As you can imagine, I'm not a happy bunny.

Less unhappy than I used to be with the earlier versions of the firmware, but still not really happy.
It is still broken, but a little less broken than before!
DLINK: Your firmware people still need to get out of the cubicles and get working on this.