There's a fairly steep learning curve in forum moderation and, IMO, the longer a person moderates on FT, the better they understand the TOS, know how to use the forum tools, get to know the forum regulars, etc. So I'm not in favor of moderator term limits.
And, since I'm running for a second TB term I'm not much in favor of term limits there either.
Seriously, TB is an elected position and it's a small group. I'm sure the FT members will automatically "term limit" any TB member they don't wish to see return.