I had bad luck with cheapo gel tape. My cinelli cork tape is really starting to wear too. I re-wrapped it and cleaned it once in 2000 or so miles, but it may be time to buy some more.
I think bar tape can last a long time if you don't care about how it looks. The key is wrapping it really, really tight, I think. Sometimes it just needs to be re-wrapped. I like the upside down electrical tape idea.
+1
Tight is critical. I make the tape have about 10% less tension than what might tear it... I experiment with a small piece before wrapping it to find the tearing point. With tight tape and the upside down electrical tape, it holds for a very long time.
I for one have had good luck with the cheap Nashbar gel tape, but have had bad luck with expensive gel tape from the LBS (although it was comfortable). Go figure...