It would be nice to extend a map. Because there could be people wanting to beat it with no time, or people who want to make time trials.
It's a double edged sword, because if you're on Lore and a % of people are shouting RTV/wanting to go to something easier, it's not really fair to make them stay on there past 30 mins. Maybe if there was only X amount of players on the server, or something.
As Kaiden said, it's bit of a weird one. I've looked a few times in how to best implement it - but I can never quite get it feeling right (eg a vote always seems a bit off) and I think to some degrees, 30 minutes generally seems to be the sweet spot.