I think it's very dependent on the project. There really are times in php-src when you want to be able to go back a fair way, since the last significant change to function's implementation may well have been 10 years ago in the early 4.x days (and Git is going to be a huge win for us there over Subversion).
I wouldn't be surprised if it makes much less sense for the kernel, though.
https://github.com/python-git/python/commit/463d099321a4572e...
(Current first page: https://github.com/python-git/python/commits/master?page=117... )
Perl - first commit, 24 years ago
Amazing title: a "replacement" for awk and sed
https://github.com/mirrors/perl/commit/8d063cd8450e59ea1c611...
(Current first page: https://github.com/mirrors/perl/commits/ams/no-more-study?&#... )
Apparently the current Linux kernel repositories don't go back as far: http://kerneltrap.org/node/13996