Ian. Cant comment about ROSPA. But I did check with the wife & she doesnt know of a time limit to take the test at all. As for observers, they are as wide a breed as bikers themselves, so have different ideas, opinions & levels. However the final goal is the same. During my "guidance" I was told conflicting methods, had some really good observers & some that Iv never bothered to ride with again. But it did make me think a little more & understand what they meant.
In my 8 years of riding (my 1st Christmas pres from the now wife was to take my bike test), I have only ridden with advanced riders. We regularly take a few trips to mainland Europe & have just come back from the Pyrenees (on the RC8) with a few of our mates (11).
So I feel sorry for the guys I meet who only ride their bikes for a couple of hours on a sunday on their lonesome whilst putting IAM achievers down.