I've learnt plenty of songs for various bands that never saw a gig or only made it into the wild once. Sometimes things don't work. I've even learnt entire set lists for one off, dep gigs and never played the songs again. Yes, it can be irritating, but it's focussed practise that only serves to make you a better player. I have a gig with a new band coming up and I've learnt all the songs they sent me. Turns out that we didn't have enough songs for the initial gig and some numbers have been thrown in for padding, two of which will not be played by this band again as they are off genre (harrumph!). Add to that these two songs are by a band I have little or no interest in. Nonetheless, it has been good practising them as it has sharpened my ears and reminded me that online TABs are often wrong and really wrong.