"Once you have the rating you are expected to use your own common sense in deciding how to use it."
That is such an important statement.
As we all know the aviation industry is probably the most regulated of any.
Doctors, dentists, lawyers, accountants and a host of other professionals are not tested at interval. I appreciate if they have any sense they will undertake ongoing professional training and in some case are required to demonstrate they have done so to their regulatory authority. I also understand that in some cases there is an effective ongoing peer review.
As has been commented in the States no revalidation of an IR is required if you meet the currency requirments. In the UK revalidation is required every 12months. The States have always had a biannual review, for years we have not. Is there evidence that revalidation improves safety, is there evidence revalidation should be every 25 months, every year, every six months, every .. .. .. Where do you draw the line if a line should be drawn, and do you draw that line on some arbitary whim - once a year sounds good, and will go down well with the examiners!!
I have a pretty high regard for peoples common sense particularly if they have shown the ability to become a pilot and go on to get an IRing. On the whole if people are not current and have in the first place been properly trained to understand the risks of not being current they will go and get some training and certainly will not be shooting approaches to minima. Of course there will always be bold pilots and I suspect with all the currency checks in the world there will still be bold pilots who are prepared to exceed their own currency abilities.