If I never connect my Windows 7 laptop to internet and never use USB thumbdrive to copy files into my laptop.
Do i still need to do security update from time to time? And install anti-virus security suites?

Normally I will use Windows 7 to do work, key in data from hardcopy, do excel calculation/graph and do microsoft word documents.
After finish work than burn the files to DVD and move the DVD to a Linux PC which is connected to internet and send the data files to boss. (I work at home).

The reason i follow this procedure is because i don't want to wast time to do security update (both windows and anti-virus) and save the annual anti-virus fee. ( and I heard that some malicious software are so advance that no anti-virus is able to detect them and clean them.)

Of course it is important to use the latest Linux.
Just downloaded the latest Fedora 17 and the latest Firefox.16.

The reason is because my Fedora Linux is connected to internet all the time, but never connect Windows to internet except the 1st time after reinstall windows when do activation.