Our singer is a karaoke queen. Luckily she had some band experience previously but she still goes out and sings karaoke every week. She actually uses it as a marketing tool for our band. She tells everyone there to come check us out to hear more, and she is really good (and really good looking so naturally everyone wants more lol)
This is good... IF the karaoke is helping her maintain/improve her voice on band "off nights" and IF the band is always priority 1 for scheduling.
It's not so good at the point her voice craps out from over-use and/or the band's gigs or rehearsals take 2nd place as in the OP's case.
Kinda reminds me of the pro football players who play pickup basketball in the offseason... it's all fine and good until they blow out a knee on a playground someplace.