I'm guilty of this as well, though now I'm tempted to go back even further and remake some of my first characters from when I was 12-13.
The thing I'm really chomping at the bit to do is run a one-shot epilogue to my last 3.5 game in 4e, remaking all their characters (with the Psion, I can now make the entire party) in the epic tier for one last grand adventure.
Guilty of it in Past Editions. Haven't done it yet in 4E, mainly cause not a subscriber and don't have the books.
But I will admit I would do so just to see it.
It would be tempting to port the one Wizard I converted from 2E to 3.5E mechanics to do both a 2E to 4E and a 3.5E to 4E conversion seperately just to see how widely varied it is between them.
I know I have a few 1E characters floating around as well that could be fun to do so.
I have a Star Wars character that I originally played in a homebrew White Wolf Storyteller system. From there, he's been played in the WEG d6 system, and all three Star Wars systems. So yeah, been playing him for a while.
What I have discovered in the process is that each time you convert, you may lose a little something, but you also gain a little something. The key thing is to go with your themes. Your character won't look 100% the way he did in a prior edition, but those themes will give you a fair approximation.
Remember too that characters are part story and part mechanics. The story remains the same. So if you follow those themes, and recreate your character through the lens of the new edition, then you should come up with a fairly good approximation.
Guilty. I've done my first ever D&D character, an OD&D Fighting Man, into every edition of the game including 4th. But I've got a habit of taking characters who I found interesting to play and creating stats for them in other games, just to see how it works out. Sometimes I've used them with different names as NPCs, if I like how they turned out.
Not only my previous characters, but I tried doing D&D versions of the cartoons I grew up with, like Lion-o and She-ra. The character builder was the only reason I got DDI. Everything else is just a bonus.