I think we need to take a bigger view of the issue. The recertification idea carries sounds great but makes a few assumptions that are most likely not correct.
1. An active instructor is not neccesarily a good one. in fact pressure to generate student numbers can get the opposite effect with instructors recruiting minimally interested students and pushing them through a course to meet a quota. And it is a further disincentive for instrucotrs and LDSs to spread an OW course out over several weeks, take it slow and do a better job of instructing. Finally, I'd argue that if an instructor is truly qualified (ie. has excellent in water skills AND can actually efferctively and efficiently impart thse skills to others) they will maintain that ability whether they teach on student a year or 100 students per year.
2. An active diver, diving to the maximum level of their training to meet a quota is not always safer than an active diver who just dives a lot. I am a cave diver and while I am certified to dive in caves, do cave dives involving complex navigation, stage and deco gasses and to do so below recreational depths, not every cave dive I do should be to that maximum limit. And while the skills are perishable, they can be effectively maintained with application and/or practice at shallower depths and lesser pentrations.
3. Currency quotas can have a paradoxical effect. As Trace pointed out earlier, meeting a quota can provide an incentive for divers to dive outside their comfort or ability levels when the opportunity arises - on days when they may not be prepared to meet the demands of that dive, but are pressured to do so by the rest of the team needing to meet the quota. What matters is not that the diver frequently does dives to their maximum certified limits, but rather that they maintain the skills needed to do it and then, before they do it, that they knock off any rust and work up to that pinnacle level of performance. That is an entirely separate issue than having x number of dives in x number of years.
4. Rules won't cure stupid or improve poor judgement. It does not matter whether a diver has a "current" cert. What matters is that the diver knows and respects their abilities and limitations and dives within them. That involves making a personal committment to ensuring their skills are current enough to meet the demands of any dive they are undertaking and working back up to that level of proficiency if their skills have slipped. A diver does not magically get worse at, for example, 3 years post cert. Their skills are no better at 2 years 364 days than they will be at 2 years 366 days.
5. A requirement for diver recertification will not solve the "divers with poor skills" problem. Poor instructors and poor LDSs turn out poor divers and if you impose a recert requirment, guess who will be doing the recertification.
6. Increasing the cost of initial certification will not keep out the less interested. It will keep out those with less money, so the remaining poor divers will have higher average incomes, not higher than average interest. Adding a recert requirement will just add another financial burden and reduce the anount of real diving a diver can afford to do. The dive industry is already badly skewed by the dive travel industry and local diving has all but dried up in most areas. The result is a large number of divers who only dive on 1-2 trips per year.
7. If you really want better divers, you need higher levels of currency and skills proficiency and promoting local diving is the most effective way to achieve that. So instead of focusing efforts on recertifcation, focus efforts on the local dive shops, local clubs and the social side of diving to encourage more people to get in local water more often to develop and maintain skills.
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For pilots with less than a specified number of hours, the FAA mandates a bi-ennial flight review. This involves some instruction every two where a flight instructor essentially evaluates your skills and essentially signs off that you still meet minimum standards. For an active pilot this might inovlve one hour of instruction. For a less active pilot in need od substantial skills refreshing, it may involve several hours of instruction.
Just as importantly, once certain certification levels and/or experience levels are reached, the requirement no longer applies. The underlying assumption of the BFR exception is that once you reach certain training and/or experience levels, you ought to know enough to fly within your limits and to know when/if you need some refresher training.
The FAA also has some minimum currency requirements such as a 3 take offs and landings in the last 90 days before carrying passengers and a similar requirement for night flights.
A combination approach is used to maintain currency for instrument flight with the bulk of the responsibility staying with the pilot with instruction only coming into play after an extended period of inactivity.
In a sense, some operators in the scuba industry use the same approach - resorts that require X number of dives in the last year or boat captains who may review a divers certs and logs to determine both training level and currency before taking a diver to a specific wreck. In my opinion, that type of approach makes far more sense than arbitrary quotas and time limits.
