Some sites, like BP or P411, signify when an account is closed.
Others like skipsweb and myprovider do not.  This makes it impossible to clean the board of links to providers that are no longer valid.
TER could easily cause links to sites that do not close dead accounts to expire in two years. It would improve searching for active providers considerably

On the main search page (top), there is the "Exclude Bad Websites" option. Does that do what you want?  

Also, some websites do go stale even if the lady is active and advertising elsewhere or with a newer ad on the same ad site.   Hmmm ... no, you want links to the perpetual ad sites to terminate after 2 years or so. But what if she is still active and WANTS her free, no maintenance, perpetual Skipsweb or other ad to remain "active" and even DEPENDS on such a free, perpetual ad as her main ad?  

If a perpetual ad link goes into her Profile on Day 1, and does not change, your clock will start ticking and her link (or her Profile, too?) will disappear after 2 years. But what if she has continuing, fresh reviews for the next many years w/o a new ad link? Is your 2-year clock linked to the perpetual ad or to the most recent review?

How about a "website filter" where you can enter one or more domains that you want to exclude or include

The problem is the web crawling sites that harvest ads from other locations and then leave them up.
This has nothing to do with a provider's preference or activity.

The "Exclude bad websites" button does not work the way that you say it does.
  It only is flipped to bad website after a TER member makes a problem report the weblink as bad.  It is not a auto test by TER.

I had stuff ABOVE the quoted text and BELOW the quoted text.

No argument about "exclude bad websites", at least not what TER has now. Read BELOW the quote and tell what you think or how your suggestion should or would work.