[MJM]

It doesn't necessarily have to be structured in a democratic fashion, or in a method in which a 'board' of directors appoint someone for a fixed period of time.
A person could simply say ... "well ... I'm willing to do it for a year" or whatever.

As owner/admin, I remember thinking that what I was embarking on would be a 10 year project, though looking back at things that I've been involved in during my lifetime it seems that things happen in 5 year increments.
(started forum in 2000)

Thing is ... I never openly told anyone this at my site (yet), and think perhaps it might be a good idea to begin hinting that there will come a time for a replacement.
As owner + admin + mod + etc I've been 'wearing too many hats', and letting it be known that some of my duties have an expiration date may help others realize that I'm not immortal, and encourage some to hone their skills for needed positions.

... just chewing the cud so to speak, and interested in hearing others experiences.