mavnroxy,
If you want ease of editing, stick with MiniDV. It's the best tape format. If you want small files and you're not doing to much editing, Hard Drive and DVD cams can both manage this, but again, editing is a real P-A-I-N.
Hank,
I typically keep the original tapes from a wedding for somewhere from six months to a year, depending on how much they spent. I figure much later than that, and they're either happy with their final edit or divorced. It's come in handy a couple times where a couple comes back a few months later and asks if we can make a different version for a family member. It's like fire insurance. You don't need it, but you never know.