I've raised a feedback support request for the developers to look at it. I can cope with the 30 minutes (although if that happens at a time I'm working, that'll be frustrating), but 15 minutes is too short.
Luckily I am at home, but I'm not happy that I have to waste 2 tokens to change a kick-off time when they leave me no choice (especially as I can't do it on my phone and because tokens are very hard to get at the moment, since no videos are showing up)