Well for 90% of the RAA fleet it is probably a fairly accurate comment, I know on mine if I get an engine out it would have to be a seriously thermally day to keep up there for too long. I work on a rough figure of 10:1, I am not sure of what the 'average' glide ratio of recreational aircraft is but I would be surprised if it was above 15:1 so I would say for the majority of us that the engine is the main thing that is 'keeping' us up there.