Mine keeps getting much the same. I ought to do the @swarden43 wax and twist, but I'm low maintenance. Double-A battery in the trimmer and a mirror keeps it presentable. When I start tasting my morning coffee in the afternoon I know I'm past trimming time.
Funny... I have the same standard with my goatee... if it gets wet while drinking, it's time to trim.
Going for a walk and smoke near my brother's house in County Durham. Two Yankees in the British country side and enjoying fine weather.