They say on the top it's bad weather no more than 14 days every year. I've been to Big Island 7 days and the tour was cancelled twice, 6 days of bad weather in a row... I looked at Mauna Kea forecast and spotted a night with 5% mist, started to look at every agency but nothing. Was thinking to rent a jeep and drive there myself, but was afraid of 0 - 4200 meters altitude in a single "jump". By fortune was recontacted by a tour operator in the morning of the good day and there were 2 seats left. So it felt more an achievement.
I was ready to write a topic: "7 nights at the bottom of Sag A* and didn't even see it", but the wheel turned for one time!
BTW for everyone interested, it seems that all the 14 days are in august, you have been warned.