Aquanaut4ata:A couple of questions mentioned: Can you go back once you let your DM certification lapse? With SSI, you have a choice of being "Active", "non-renewed" or "retired". Active is of course active. The other two are not. You can return from both, with varying requirements, such as updated insurance, back dues, current materials, refresher training, physical exam,etc. I would assume that most other agencies are similarly aligned.
Another thing mentioned was carrying insurance if you're not actively functioning as a DM. If you have at some point been active, but are not any longer, you can purchase "Trailing insurance" at a much lower rate, which is designed to protect you on statute-of-limitations issues. I believe that it is reccomended that you carry it for 7 years.
Exactly...PADI is the same way.
Non-ACtive DM's/Instructors can go into inactive or retired status. In order to renew status, the requisites are different depending on how long you were iinactive, why you became inactive, and varios other factors.