duct tape has worked for me in an emergency to get home, but still went flat, but just not as fast.
some things you don't wanna do to a bike:
1. duct tape as a permanent tire repair solution.
2. using a piece of steel plumbing pipe as a seat post. (guilty of this one myself in a fix)
3. use shifter cables as brake cables. they are thinner and not as strong.
4. pack a s.a. igh hub with grease when it calls for oil.
5. ride a bike with a cracked front fork (OR FRAME)
6. run a multigeared cluster on your rear wheel as a single speed without any derailleur or tensioner when they make single cog freewheels (and if you call it a fixie, i smack you)
7. use duct tape for handgrips.
we have all seen #6 and #7 and its time for that to just stop. i did #2 with alot of extra pipe in the seattube and believe it or not, sized perfectly with no freeplay and not too tightly as i could ever get out. if only bikes came with seat posts long enough for people 6'3".