SummerTime and Amp Heat

05-30-11: Willland
I too run a fan to draw heat from my B&K EX4420. My amp is the older model of your Ref2220. It draws 75 amps of current peak to peak .......

Noooooo! it does not draw 75A p-p all the time! The amp specs might say that it is capable of supplying 75A peak but the amp does not do that unless the load requires it. The 75A peak is just the max capability of the power supply transformer & capacitor bank to supply that much current.
it runs warmer to the touch 'cuz the bias is on high(er) side (to perhaps make it run longer in class-A before switching over to class-AB).

see if you can find out what at temperature the specific B&K model is supposed to run - if possible. Then make sure that you are operating it under those specified conditions.
For ex, many of Pass' designs (specifically the older Thresholds) were meant to have their heatsinks at 52-54C. That was supposed to be normal operating conditions.
FWIW.

05-30-11: Hifihvn
The links are to long to post. Just Google capacitor life shortened by heat.

True Hifihvn that cap life is shortened very quickly by excessive heat BUT.............just because the heatsink is getting hot does *not* mean that the power supply caps are getting hot! Depends how the amp is made & where the power supply caps are w.r.t. the power transistors & heatsinks. The OP says that he's drawing heat out of the amp which presumably means heat from the power transistors only. The power supply caps could be very cool if the amp has grates on the top-plate, bottom-plate.
Cannot assume that power supply are automatically hot if the heatsink is hot.....

05-30-11: Tripper
No one seems to have mentioned the associated load on the amp and its output stage[s]. As a corollary, one sometimes sees ads that say "drove my Thiels/Apogees/'stats with aplomb". That's all good and well but it would seem that driving the amp to its upper limits might shorten its useful life and perhaps wear it out faster than one would with an easier load. Just wondering...

all (larger) power amps have output protection circuitry ( that kicks in if there is unusually high DC offset) + thermal shut-down circuitry that cuts off the output power stage if the heatsink temp goes too high (this is often monitored by transistors attached directly to the heatsink & the bias running thru these transistors is set to the upper limit of the heatsink temp that the designer thinks is safe) + the power transformer is also designed to provide lower current than the transistor's max so that the transistors always operate in their SOA. All these safety checks (idiot-proofing) ensure that (unless you short the speaker binding posts) the amp will operate safely & within its limits 99% of the time.
So, if the amp is driving somebody's Thiels/Apogees/'stats with aplomb then it is doing so within the SOA region of the output transistors (otherwise it'd be shutting down time & again & the owner would not make such a statement).