Bought my new stihl hedge trimmer and used only 4 months or so and had to bring back to dealer for service. Dealer said carb was bad. He said that I should not be putting any fuel in it that is older than 2 weeks old. Even with fuel stabilizer . Never new that. I run pure gas in all my handhelds. Is this true? I figured I should be able to go a least a month or so on fuel. Let me know what you guys think. I do have a commerical 2 year warrenty but does not cover the $65 carb. They only cover the carb for one month after purchase.