I don’t think energy is youthful — a lot of fighters bring high energy to fights past their early 20s. And a lot of fighters with power have long shelf lives.
I think energy is about youth when it comes to the high energy of a Tyson. I remember a fighter in the 1980s named Frankie Warren, who fought McGirt two times.. Just had a whirlwind style which overwhelmed guys, yet he didn't look like he could punch hard.. Soon his style wore him out and McGirt won the rematch, a combination of Buddy learning some things and Warren wearing out a bit from that style. That is my take on it. That is all we give on here is opinions, beyond that what is the truth? Tyson to me had this style which after a few years was harder to naturally exhibit, which is why he was hit cleaner later and didn't utilize his head movement in the same way.
Definitely ended with the Spinks fight, as that was his last outing with trainer Kevin Rooney. As for which fight it started with, I would say the Biggs fight. So all of Prime Tyson's fights were: - Biggs in Oct 1987 (won by TKO in R7) - Holmes in Jan 1988 (won by TKO in R4) - Tubbs in March 1988 (won by TKO in R2) - Spinks in June 1988 (won by KO in R1)
With Mike Tyson, the number of years when he was in his prime does not tell, but what he showed in the ring. If we are going to look at the prime when his form (his H2H) was constantly on the rise - 1986-88. Already in 1989, the undisputed lineal champion Mike did not have that "hunger". In 1990, he relaxed too much, but he tried to come back. He succeeded to some extent, and the prison finished Tyson's return to the prime.
He was very good from 86-89 (but gave even greater image). People can't accept that outside of that relativity brief period he wasn't ever the best in his division again. Yet people still overrate any iteration of Tyson still despite all logic.
It is impossible to pinpoint his exact prime because everything depended on how he trained—and that varied quite a bit. For instance, Tyson himself admitted he was completely unprepared for the Tucker and Tubbs fights—and Buster, of course—while he was dealing with a venereal infection against Berbick. Even so, he looked great against Berbick and Tubbs, though those were short bouts. He was in excellent shape against Alex Stewart, but by then he was likely a technically inferior boxer because he was sparring much less and doing less work on combinations and defense. His best performances were against Biggs and Holmes. That represents Tyson's prime: the turn of 1987 and 1988.