I don't think we should encourage or discourage interims. I think we should just make it clear that they are part of a WG's toolkit to use as appropriate. For a new topic with a lot of issues to discuss, a two-day f2f interim can make as much progress as a year of "normal" IETF discussion. For an ongoing topic, a two-hour virtual interim can be enormously useful, but cuts out people in some time zones. I agree that nobody should fly to an IETF week for a two-hour meeting. In my experience I fly there for about 50 hours of meetings; that's the point. Brian