Stanley Ketchell was a pro for what, 6 or 7 years? Same as Pancho Villa. But they packed in a fair few fights. Michael Spinks only had 32 fights
There will of course be a whole raft of fighters who were successful and who had their careers cut short for one reason or another beyond their own control, guys like : Terry Marsh / Zack Padillia / Harold Knight / Lamar Parks etc Er..Legal Incarceration will of course be another reason (albeit James Scott springing to mind ) Fighters who walk away whilst successful are no doubt much rarer, and may of course have other pressures Lazlo Papp (political) and Jamal Hinton (religious) spring to mind. Some ex star amateurs probably get a rude awakening in the pro ranks, No Headguards, 3 minute rounds, longer distances, and Pro "Ruffians" trying to disembowel them and take their head off.... who drift away with projected success unforfilled. - its a rough old game for sure.
Not counting the Johnson comeback in 1910, James J. Jeffries had a highly successful career from 1895 to 1904, having just over 20 pro fights, winning the title in his 13th. Also, Rocky Marciano's pro career lasted from 1947 through 1955.
In pro' boxing, Saensak Muangsurin. WBC champ' within 3 fights, and two top ten ranked fighters in his two fights before that. In '77, made seven defences.
Gomez comes to mind. Not a particularly long career, although half his fights (Or close to it) were title fights.
Even by classic forum standards it surprised me a little 2d bad 2c it took so long until Salvador Sanchez was mentioned . 4 that he deserves another mention here .