In Adelaide we do pretty much the same thing as everyone else, start at 6.15, go till 9.45 or 10 usually, three rounds swiss, last three or four gnks have had between 16 and 18 people, though it used to be a bit less. We used to do 65 minute rounds but will be trying out 55 minute rounds to finish earlier, and encourage people to learn to play a little faster as well. We are generally fine with the fact that SOS sometimes lets some people who might not always win still do well and grab some of the better prizes, it's all pretty casual, and still has a bit of a learning environment and laid back feeling for the most part. You usually get a bunch of people on 5-1, in some events you get the top 6 or 7 players on 4-2 which can be meh, but that's it, no one takes it so seriously that it's an issue.
We do cube events as well, roughly the same time frame though drafting and deck building can take almost an hour so it can drag on. Three rounds, same start and finish time, rounds are 55 minutes, maybe? But could be shorter. Maybe they are 40 minute rounds, actually. 30 card deck sizes btw (minimum) and first to 6 AP.
We do leagues as well but they are for fun, and people play their matches at their own leisure. No prizes other than....prestige? An invisible crown? I dunno. But I think this has all worked fairly well so far for our local meta, illustrated by its recent growth