Depending on the type of petrol you have over there (mostly ethanol here), long term exposure to products such as ethanol, alcohol, etc is known to deteriorate parts such as needles. This mostly happens when the mower, etc is not used on a regular basis such as storage for 30 days or more. To extend the life of your needle, I would recommend you turn off your new shut off valve and let the engine starve out (don't forget to turn the key off afterward). Some folks may inevitably disagree but I have seen this happen to a few folks including myself.