Let me clairify just for a second what the hobbyshop guy is trying to tell you. When set up properly you should not have to touch the needles very much. But, you have to get the engine setup properly first. Once set properly you will hardly have to touch the low speed needle. All you will have to do is peak the high speed and set it a little rich on the first flight for the day. The pinch test works great for this. On the low speed needle when set properly you should be able to idle in the 2000 to 2500 region all day without dieing or loading up. After about 8 to 10 seconds you should be able to smoothly roll the throttle (1 second to high throttle) to high rpm without any hesitation Increasing the idle speed only compasiates for an incorrectly adjusted engine and makes for a plane that will not slow down on landing. When the plane is setting there idling you should be able to tell what it is doing. If it starts to loadup and slow down it is rich. If it starts to speed up it is lean. Adjust the low speed needle or air bleed to correct this. Turning the air bleed clockwise will richen the mixture and counter clockwise will lean. Remember the low speed needle affects the high speed setting but not the other way around. You have to learn to setup an engine correctly, just leaving the engine alone will not do anything. An incorrectly setup engine will not fix itself.

If you keep having problems with landing speed switch to an 10x5 prop to slow the plane down on landing.