I am disappointed in a router if it needs rebooting without me having fiddled with it first.
Currently my router has been up for 7 days, and that only because I was playing with the firewall and connection settings last weekend, prior to that it had been on for over a year (in part due to the UPS it is connected too).
I have only had two routers that needed regular reboots.
A Belkin router, and a Trust router.
The trust router was stable enough until I started trying to do to much with it at once.