So, I've learned many things in the years I've been riding. One of those things is that most riders who say they'll "be there," won't be there. It's basically a given. If there's one thing I can depend on, it's that if 40 riders say they'll "be there" then I'm lucky if one shows up. Screw that.
Therefore, my wait policy (aka kickstands up at) is 5 minutes. Not 10. Not 15. And sure as hell not 30 minutes. That's wasted riding time. My policy is simple; if you're not there in 5 minutes then I won't be either.