Willie, I awould also add that the 'Checkers' should not necessarily be the most senior - which tends to be the trend. It takes much more skill and knowledge to TRAIN then it does to check. This is proven everyday in many countries where the Transport authority has inpectors/checkers who don't even fly the aircraft hey are checking on (at least not on even close to a regular basis).
Keeping the motivated and skilled trainers is essential.