With proper revision control you should follow the maxim of 'commit often', and I certainly commit for every bug fix or feature implemented. That can be several times per day. With appropriate log messages you get a fantastic trace and you can roll back to any point. You also tag important revisions like releases, betas etc.

The diff utility is brilliant, and can also do M$ Word files.

By storing all versions in an optimum format you save disk space compared with zipped copies.

I also use command line utilities to embed a revision into my source so I can check what source versions went into a build automatically.

Subversion is free to use, and saves time and stress. It makes manual processes seem incredibly slow, error prone and inefficient.