There is a debate regards to the best way to maintain a large website with 10,000 + web pages (school related) how to maintain the site to allow global changes (header, menu, footer).

All of the pages are currently designed in htm built using Dreamweaver template. The downfall of maintaining the site using this system is that when you make changes to Templates (Master or nested) templates on Dreamweaver, you have to upload every file on the site using the template.

I am looking for other alternatives (if possible how to maintain the site with global change option) keeping the htm file extension.

Ideas? If you would prefer to use serverside includes such as asp, php, or shtml do share, and tell me why.