A Markov chain with transition matrix $P$ is termed regular if for some $n$, all entries of $P^n$ are positive.
Is there a known notion of degree of regularity quantified in terms of how soon all entries are positive? That is, a Markov chain with transition matrix $P$ would be considered more regular than a Markov chain with transition matrix $Q$ if $P^n$ has positive entries but $Q^m$ only has positive entries for $m>n$.