How can I remove all messages, save to a DVD, and access them easily later?

Question

I recently dropped my .Mac account in order to use Gmail full time. I would like to be able to take those mac.com messages off of my computer--preferably saving them to a DVD--so that when I activate my Gmail account in Mail, they would be totally separate. I am also trying to save hard drive space.
I've looked around about this, and even downloaded some Applescripts for Archiving mail, but those seem to continually make Mail crash (I have 3 years worth of email saved in Mail.app--about 3,000 emails). I have read enough about Backup to know that it saves things in strange/proprietary ways.
Is the best plan simply to copy that ~/Library/Mail folder, straight up to a DVD, and then clear it off of my Mac? How do I do that without making Mail.app unstable? And will it be difficult to then read them from the DVD later if I need messages?

Answer 1

... and import its contents back into Mail whenever you wish ...
You can also open individual .emlx message files within the copied mailboxes to read them, without first importing them back into Mail. However, by itself this isn't very practical because the files have names like "12345.emlx" that offer no clue about their content, so finding the message of interest among 3000 of them is a challenge.
You might think that Spotlight would help with this, but in its normal state it excludes .emlx files from searches, so you can't simply do a Finder search on subject, content, etc. There are ways around this but none are simple:
1. Use a Spotlight "raw query" search to find the messages. This avoids the exclusion of .emlx files that is tacked onto all normal Spotlight queries but requires knowledge of the syntax of raw queries. (To get an idea of how that looks, & to see the exclusions, you can do a "Get Info" on a Smart Folder. The raw query string is listed after the "Query:" entry in the General section.)
2. Replace the ".emlx" extension with ".txt" or similar in the copied messages. (This could be done with an AppleScript using Finder.) Spotlight will then include the files in searches. In this case, opening the message file by default will be with TextEdit or similar, so you won't have access to "Reply" or similar features of Mail, but you will see the entire message, including the preference-like xml info about it that follows the message body in the raw .emlx file. As long as you don't alter the content, you can reimport the message into Mail by changing the extension back to ".emlx."
3. Mimic what the Mail archive utilities do & construct a database that either relates the numbered .emlx files to their content or import entire files into database records & use its search features to find the messages of interest. This is appealing if you have a powerful database app like Filemaker & skills at database construction because you can construct any view of the info you want & organize it however you like. Obviously, if you don't, it would be simpler to buy a utility, which may offer other features that you might find useful.
These alternatives would be most useful if you need to avoid reimporting large mailboxes back into Mail because of disk space concerns. They also avoid the perhaps considerable time it would take to reimport thousands of messages just to find one or two of interest. The second & third ones are somewhat self-contained & independent of Mail itself, which is both a strength & a weakness, depending on your needs.