Yeah, frequency is the more important the shorter the stops. In Budapest, I am used to suburban buses with at most 20 min off-peak-hour and downtown buses with down to 3 min peak-hour headways (but no one thinks of calling it BRT). In Brest this summer, I thought of taking a bus from the station to the bike race control point in the suburbs, but the 30 min headway around midday made me walk instead. *Lunatic*, n. One whose delusions are out of fashion.
Of course, for that to be effective in recruiting new riders, as opposed to just a convenience to existing riders, those who are not using the bus has to know where they can catch the bus and have an idea that it goes somewhere they normally go, which is where the clearly branded, high visibility bus stops ... sorry, "BRT stations" ... are an essential complement. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.