With normal care it would be extremely unusual for a second stage to become plugged in recreational diving. It does happen on occasion with divers who drag their octos around for numerous dives with no post dive rinse and no pre dive check, but not in normal use if the diver has any clue at all.
Cave divers seem to like the ability to remove the second stage cover and diaphragm to remove rocks, sand, etc. This is a possible occurrence for a diver scraping through confined area in caves so it makes sense in that application.
It should be pointed out however, that a diver in a cave dissassembling the second stage is in much more controlled conditions than a diver would be in open water where parts could be easily dropped or carried away by the current.
The counter argument is that nothing entered the reg that is not too large to leave by the same hole (the mouthpiece) so in all but the worst cases the majority of the debris could probably be shaken and/or purged back out.
Another possible option for open water divers would be to only tighten the LP hose connections to the second stages finger tight. This would allow a functioning second stage to be swapped from one first stage to another as long as the valve was off to each reg as while the second stages are removed.
This could be done if a defective second stage is encountered on a stage or deco bottle and would allow one functioning second stage to be used with multiple deco or stage bottles to access all the gas in the various tanks during the dive. A complete second stage is less likely to be dropped and no small parts are involved. It requires that all the second stages are set to operate with the first stage having the highest IP (to prevent possible freeflows) and preferably that all the first stages are adjusted to operate at the same IP so that none of the second stages have to be detuned to work with their normal first stage.
The main downside though is that some care is needed to ensure the second stages do not unscew during the dive and be lost and, in the event the air is on to that second stage, result in rapid air loss. Pre-dive checks are a must as a finger tight second stage will normally unscrew slowly over the course of a few dives.
But in short other than post dive preventive maintainence, pre-dive checks and shaking/purging the second stage, none of these techniques have any useful application in recreational diving and potentially cause more problems than they resolve.
