Change from SSI values to .shtml

Top of the mornin' all - I am new to this forum and am looking forward to gaining much needed knowledge regarding SEO as my biggest challenge clearly is lack of traffic.

My first question is general in nature but I need to ask.

I have just completed a hosting change that requires SSI functions to be now passed through an .shtml extension rather than an AddHandler in the .htaccess file. Changing extensions is not a huge issue but if I change the extensions to .shtml I an going to have to have redirect 301 lists in the .htaccess miles long. This lends itself to the first question. How many redirects can be effectively managed by a spider before the file is too cumbersome and causes engines to ignore the domain.

As a corollary, the biggest issue for SSI currently is an update of the Copyright information. Since legal department automatically ensures dominion over copyright, a script is used to automatically roll over the year only
<!--#config timefmt="%Y"--><!--#echo var="DATE_LOCAL"-->

and this code appears at the bottom of every, currently, html page. Would it be better to replace this code with a javascript code and forego redirect 301? and, if so, would anyone know how to build that code? Since I am relatively new to this type of operation, what is likely a "cakewalk" for some is a challenge to me.

Thank you and looking forward to learning.

Dylan_O