
First, the variety of rules changes under consideration:
+6-year term limits for cmte leaders (regardless of ranking of chair)
+limit floor leader and whip to one committee gavel
+delay above change for 2 yrs
+subcmte gavels: prioritize senators who don't already lead a cmte
+6-year term limits for cmte leaders (regardless of ranking of chair)
+limit floor leader and whip to one committee gavel
+delay above change for 2 yrs
+subcmte gavels: prioritize senators who don't already lead a cmte
Term limits for the lead D senator on committees is likely VERY BAD. The most likely outcomes are a loss of institutional knowledge and ability on the committee, turnover of staff with that knowledge, and speeding up retirements of good members.
I submit another likely side effect of committee chair term limits is the further empowering of interests who have deep enough pockets to hire lobbyists and conduct issue campaigns. @leedrutman makes that case here. https://www.theatlantic.com/politics/archive/2015/03/when-congress-cant-think-for-itself-it-turns-to-lobbyists/387295/
Republicans in the House and Senate have experimented with these rules and they seem to have gotten all of the negatives and few positives. As @craigvolden @TheLawmakers show, term limits can make chairs less effective: https://www.washingtonpost.com/news/monkey-cage/wp/2017/01/04/how-term-limits-for-committee-chairs-make-congress-less-effective/
ANOTHER problem: as currently constructed, these rules will further empower floor leaders and centralized decision making at the expense of the rest of the caucus. @jiwallner makes the case for how cmte term limits w/o leadership term limits is harmful: https://www.legislativeprocedure.com/blog/2018/10/25/leadership-term-limits
Basically, when you have regular turnover of committee leaders without turnover of floor leaders, committee leaders are at a disadvantage, and decision making gets more and more centralized. We should want power in the Senate to be diffused.
TLDR: committee term limits are probably more bad than good. Some members are itching for these changes now because they will benefit them or they think they will help. But Democratic senators need to think about the bigger institutional picture.