They may not currently or perhaps have ever been your favourite band but they are the one you have loved for the longest period time. And not necessarily a continuous period of time, say for example it may be a band you only love every second Tuesday but have done so for several centuries. Or they may have only ever been your second favourite band but you've had a different top favourite band every five minutes. That is to say if it were possible to assign a numeric value to how much you love a band on any day and then sum these values for each band over the days of your life which band come out the overall winner? Yes 'overall' i think is the word i was groping for here. Which band is your overall most bestest favourite band evah? (band or solo artist).
Mine is Stereolab (though I've kind of got bored of them lately)