Modems keep failing

I've been a customer for 18 months and I've lost track of how many times I've needed the modem replaced.  The first few modems rebooted several times a day.  A Cisco worked for a while then 1:1 NAT quit forver.  My new Netgear CG3000DCR didn't even last a month before it started needing regular power cycling.  1:1 NAT dies, devices on different ethernet ports can't see each other, and there's no response on the customer admin interface.

What's going on?  Is each "new" modem that I receive somebody else's defective modem?  Comcast's required modem rental fee is too steep for this hassle.  How do I get a good modem that's compatible with static IP addresses?