Mozy is owned by EMC, which is the 11th largest software company in the world, so that should prevent it from just going out of business. Of course that doesn't mean that EMC gets bored with it and sells it off etc. as publicly owned company's do from time to time. Mozy also has a deal with General Electric which should help keep it going for a little while at least.
For the archival question, no I don't know if that has been suggested. They just state that their service is not an archival one, but they will take suggestions on adding it.
I have come across another service that does offer versioning called Memopal. It's $50/year for 150GB for the home version, and you can use it on all of your computers (Mozy and Carbonite I think need a separate license for each PC).
http://www.memopal.com/en/default.aspx
What type of internet connection do you have? Most have far better download rates than upload ones. Plus more and more ISP's have begun throttling users that use "too much" bandwidth.