Yes, it can be tough maintaining your bags well displayed and in tip-top condition. Regular checkups and servicing are required. Here are some tips to keep your bags in fighting trim.

You've negotiated a bagtrade. Now comes the tough part: how best to ship your precious bags to your trading partner? Here are some options, in reverse order of advisability:

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Write the address on the bag, stick on a stamp, and drop in the mail. 
Not recommended: The writing and stamps reduce the value of the bag as a collectible, and the mail carrier may be tempted to add an attractive bag to his own collection.
bullet Fold bag in several places and stuff into small envelope before mailing.
Not recommended: The creases are hard to remove. Try ironing the bag with a damp cloth.
bullet Put bag into envelope just large enough to hold it. Tape firmly all the way round to make sure it can't escape.
Not recommended: Desperate to get at the contents, the recipient may damage the bag while opening the envelope. Best to leave a gap in the tape to allow access without risking damage.
bullet Insert bag into new envelope with sheet of card to prevent folding, then write address in giant letters.
Acceptable. New envelopes are nice if you can afford them, and the card stiffener preserves the contents in mint condition. But the extra weight of card can make mailing expensive, and the giant lettering means the envelope is hard to re-use.
bullet Place unfolded bag into large, used envelope, stick on address label, then mail. 
Recommended: This is the approach I use. Saves on mailing costs, and is in the recycling tradition of bag connoisseurs.
bullet Hand delivery. Bring the bag in person to the recipient.
Highly recommended. Don't bring just one bag: bring a boxful to trade. Also enables you to exchange bag stories with the recipient, as well as check out his collection (and perhaps steal a few bags in the process).