12 years now for me I think, maybe 13, to early for math. I am not sure I will ever be able to feel like an expert, solely because things are always changing in our field. Its one of the main reasons I still do this. Always something new to learn if you burned out of one area. I do believe however you can maintain expertish knowledge for a foundation. So long as you can understand the way things are supposed to work and have a solid troubleshooting, design methodology, you can usualy figure out things in a relatively quick and sufficient manner.
Routers, switches and firewalls. Network blogs, news and network management articles. Cisco, Juniper, Brocade and more all welcome.