Is it necessary to change the caps after many years of intensive use on a Classe Audio DR3B?Is it necessary? No, unless you're having audible problems (muddy, veiled, undetailed sound).
Electrolytic caps deteriorate with time & heat & other factors -- a major factor being non-usage. You have used your amp, so deterioration is less than in other cases.
Replace with caps of same value -- or even adding coupling caps... BUT leave this stuff to a qualified tech.