unreliable facetime communication

I am a computer engineer. I have Verizon DSL service. My network consist of verizon briged box connected to my netgear-prosafe router. I have setup static ip (assinged DMZ 192.168.2.254) for my ipad. For some days it works fine when I communicate with my kids. Without any setup change suddenly it stops working sor a day or two. For testing I changed my ip on my ipad and forwarded all recomended ports to the new ip (192.168.2.99). That did not solve my problem. Unfortunatly poor company Apple has turned off their facetime test site to boost their earning per share. So I have trouble to findout where the problem is. What causes the trouble in facetime communication. I purchased the expensive ipad so I can communicate via facetime with kids. By the way Apple support is not different then any other PC company like HP or Dell except the cost of the device.

I read several Apple support posts on facetime related issues. I found many facetime users have trouble like mine. I do not see any new technical explanation from Apple either. In short Apple is equally arrogant and not ready to except his own responsibilities.

Is there anyone who can suggest based on their own experiences on facetime setup?