How do you determine the length of time a player becomes a liability?
I usually loathe advanced metrics to determine player values, but I find offensive v. defensive zone face off starts to be telling of a coaches faith in a player, and their TOI can be reflective of that. If we have a very high number of defensive zone draws, it will limit a defensive liability like Barch, for example.
Likewise, if we have a high amount of PP or PK time, you'll also see special teams on the ice for lengthy amounts of time. And a guy like Kovy can float on the PP for 2 minutes at a clip no problem, that will naturally reduce a non-special team player like, Barch...
I think as long as the top three lines are getting minutes with out an extreme deviation, the fourth line shouldn't be greatly used until we have a great fourth line like last year's run.