1/365th as Good?

So at a dinner during the Full Frame Film Festival last week a veteran filmmaker (veteran in the sense that she's made at least two features) brought up the topic of how much time went into most of the feature-length documentaries showing at the fest. There were several others at the table with similar experience, and quickly a consensus was reached: most significant docs at the fest this year took at least three years to make. Some went far, far longer for one reason or another.

Ironically, as digital video arose as the main medium to make documentary films, a lot of people imagined that it would speed things up. It does, for shorts (yes, our short was made in five days -- those were the rules and why we didn't get a lot of sleep for that production weekend) and for certain kinds of features that are based on tight scripting. Yet there is little effect on production time on most longer pieces.

(It does seem as though people who might never have had access before can now make a film -- but that might be a slowing factor too, since people have to work around day jobs and fundraising.)

Coming from the world of art (where one either schedules a show and then struggles to make work for it, or plugs away at an ongoing project and then shows some of it when possible) I'm trying to get my mind around this. Does it mean that the best projects are left out in the sun for a while, where the world reshapes them a bit, or that one waits for a last detail or twenty to be revealed, or does this mean something else?

Or is it just convention?