It's one criteria I consider but not the only one...otherwise I'd probably consider mentioning the guy in your avatar in the same sentence as Mike.
That's such a great video. Carpenter and Tyson really hit it off. Tyson was regarded as at least a top contender between '86 and '02, that's pretty astonishing longevity actually.
The guy in my avatar was never the champ, so why you would have to resort to another criteria I have no idea!
I personally rate people highly on their longevity, also their reigns as champions which are 2 different things. Tyson had incredible longevity but less of a reign. This is partially due to his imprisonment but more to the fact of his unstable psyche.
Champion in '86, ranked #2 in 2002. Good longevity for any style, for a swarmer? The best of all time for a swarmer at the weight.
In fact, Louis and Tyson were basically a serious force in the HW division for the same number of years.
Champion from '86-90. Everything after that was inactivity, lackadaisical performances, and two good wins over Donovan Ruddock and Frank Bruno.