In the current Process, WGs/IGs can be extended by the Director over and over as long as there are no substantive modifications to the Charter.   The membership should have the opportunity to review whether a group should continue or change its scope or deliverables (or to terminate).  Members can appeal the Director's decision to extend and have an AC vote on it, but it would be better to limit the total extension.

I didn't put it in this proposal, but i also think it would be good to limit charters to 2 years so we get the chance to look at where the WG is headed at least every 2 1/2 years (if a 6 month extension happens).

Current (from the draft process doc)[1]
[[
6.2.5 Working Group and Interest Group Charter Extension

To extend a Working Group or Interest Group charter with no other substantive modifications, the Director announces the extension to the Advisory Committee. The announcement MUST indicate the new duration. The announcement MUST also include rationale for the extension, a reference to the charter, the name(s) of the group's Chair(s), the name of the Team Contact, and instructions for joining the group.
]]

Proposed

[[
6.2.5 Working Group and Interest Group Charter Extension

To extend a Working Group or Interest Group charter with no other substantive modifications, the Director announces the extension to the Advisory Committee. The announcement MUST indicate the new duration. The announcement MUST also include rationale for the extension, a reference to the charter, the name(s) of the group's Chair(s), the name of the Team Contact, and instructions for joining the group.  Charters may not be extended more than 6 months after the original termination date.
]]

[1] https://dvcs.w3.org/hg/AB/raw-file/default/cover.html#charter-extension