I just picked up some champagne yeast (lalvin EC-1118). I remember seeing a post a while ago talking about using this yeast and how it can pretty much last forever with just changing the water periodically, and topping up the sugar in the bottle.

Anyone else use this kind of yeast? and how do you do it?

Not quite that easy. Yeast needs nutrients too, if you want to keep it going for extended periods. Just sugar alone won't cut it. Then you might run into sanitation issues.

I have played around with yeast used in beer-making,and it seems like it lasts longer than your regular supermarket bread yeast.

I was talking to the guy at BrewMasters and he also gave me some yeat nutrient to try. He suggested adding it after two or three cycles. He also told me that adding something like a bit of V8 juice would also do quite a bit for keeping the yeast going to extended periods of time.