I've had my heavy duty pressure plate for a almost one year, but it doesn't seem to be grabbing(chirping) when i speed shift or only sometimes when I shift fast.

I'm wondering if it's the stock disc that came with the S1 tranny. How long would a heavy duty pp last?

 

How long it will last depends on how hard you drive it. How well it grabs depends on temperature and clutch wear. A stock disc will fade when it is heated up very quickly- as long as it isn't slipping I wouldn't worry about it-