The best argument I know against this is that it shifts power toward lobbyists and all those awful "deep state" people (you know, career civil servants) everyone suddenly started being worried about a few years ago, and away from elected officials.
Abolishing term limits just encourages politicians to start thinking about "What, after?" sooner.
Not sure that's what we want to incentivize.
Cronyism and back door politics within the government are far from the worst outcomes, especially compared to private industry having more power over government officials.
It also means that the entirety of their last term is basically consequence-free. Currently a voted-out senator is a lame duck for 2 months; a "last term" senator has 6 unaccountable years to do whatever they want.
Let's get rid of qualified immunity and add stronger protections against eminent domain while we're at it. Also, we need to address corrupt judges, we have very few legal mechanisms for that.
I would like to drastically claw it back but I think there are limited circumstances where that immunity should apply.
At the very least, criminal immunity and being required to carry large insurance policies for civil damages. Paid for out of pocket and underwritten based on their job performance/complaints.
Police are people and people make mistakes, this needs to be recognized on some level, but QI as it is now is positively un-American. We're supposed to have checks and balances and recourse for misdeeds. Nobody should be above the law. You literally need circumstances like those surrounding George Floyd to hold police accountable in this country.
2A was supposed to be insurance against nonsense like this.
We have term limits in several places (including California), I think TL proponents should make their case based on how that has worked out rather than pleasant hypotheticals. One downside I've seen is that it promotes a sort of legislative ladder-climbing mentality where ambitious legislators are primarily focused on using their office as a springboard to the next level of political power, and incentivized to propose changes with quite short-term payoffs.