Two angles here, and both have been discussed.
Forums- Open to anyone and all are welcome to participate. That's why this is a Community and what separates FJ from the rest. The more you participate, the more you become entrenched in what goes on here, and by doing so, you accrue equity for the future.
Milestones- Once you achieve something (Bronze, Gold, FJA) those anniversaries are big. And once you hit 'em, you've earned 'em. However, not unlike the airlines rewards systems, to continue to leverage the equity you have, you must continue to participate to a certain level.
As Chris has said, if you hit FJA, you need to contribute a certain amount over time to continue to maintain that status. Could be minimal, but still needs to be something. Will you show up on anniversary board? Maybe, but after a certain period of inactivity, you should, IMO, gradually migrate off.
Remember, many come here to ask questions and then they are satisfied and move on. And that's OK. Many want to be part of the bigger conversation, and become fixtures. Some come to become FJA, go to an event, and then move along to the next passion. All are fine so long as everyone is held to the same standards and then let the chips fall where they may.