I wonder whether I am the only one using a persistent timer as a reminder for fuel tank switching?

According to my planes POH 30' intervals are mandatory, but on long hauls 30' - 60' - 30' is a popular scheme. I often switch later/earlier due to the habit of always trying to change fuel tanks in gliding range of an airport, over the alps in particular - therefore I don't follow the timer religiously. Fuel gauges reading is notorious unreliable as well, stating full & empty works reasonable, and in between the display is nonlinear mostly. Information about how much time on which fuel tank would be an extremely valuable information.

What I would like to discuss, the introduction of a fuel tank timer simply stating 'how much time on a fuel tank' - some sort of reversed (counting up) chess timer maybe. 

-mike