As for archive, it only deletes them, not moves them to another folder/PST that I can back up. Mailstore would just create yet another file. Why would I need that? I use Microsoft's own Personal Folders Backup, and it works perfectly to back up the PST. I need to move all those messages to a separate PST for archiving.
It doesn't delete the email it creates a new PST file (or uses an existing one if you choose one that exists) and moves the archived emails there - effectively a copy to a folder then delete operation. You can also move other stuff, such as calendar, jnotes. etc. into the archive PST file). You can also create multiple archive PST files if you want and move them year by year so you have an annual archive or whatever.
The reason I suggested MailStore is because I used to use archive to do the above and now find MailStore much more convenient. It has none of the restrictions of PST files for emails and it means you have a complete archive of all of your emails in one place which is fully indexed and quickly searchable (much faster than Outlook search).
Yes you would end up with extra files on your system but so what? Disk space is cheap and MailStore provides a free excellent way of maintaining a useful complete archive whilst keeping Outlook lean and mean. It also means you don't have to open archive PST files in Outlook (and remember to manually close them again) which is a pain and leads to Outlook crawling again.
It's up to you though.
There is a simple rule structure that you could use too:
If mail arrived in specific date range move it to specified folder (can be in another loaded PST file - ie. effectively archive it to a folder)
Note you can run rules like this on a specific folder and specify a specific destination or you can run it on the whol folder tree in your main PST file and have it move everything to an archive folder.