I'm in the middle of addressing baby announcements and I'm a little anal about not making mistakes because I ordered the same number of envelopes as I did announcements. The stamps I purchased, a comic book theme, is a little big for the envelopes and because I don't want to write the address and then find that the stamp covers it, I'm placing the stamp first and then writing the address.
So when I realized that I made a mistake by addressing a card to the wrong address I was pretty pissed at myself because not only did I lose an envelope, but I lost a stamp too! You know they're 44 cents!
Luckily the sticker adhesive didn't stick too well and I was able to remove the stamp and place it on another envelope but I had to discard the envelope and get a new one.
Is it the end of the world? No. But now I have to hope that I don't run out of envelopes.
When you're ordering envelopes for your wedding invitation it is very important that you order extra envelopes -- 15 to 25 should be enough. This way you won't have to worry if you make a mistake that you'll come up one envelope short.
And you may want to order a few extra sets of your wedding invitation in case one or two get lost in the mail and to save one as a keepsake.