re capping

Electrolytic caps kept fully charged will function perfectly well and not degrade!

Nope. There are multiple mechanism for electrolytic capacitors to degrade. We once replaced 7 million of them.

The only way to properly test caps is to pull them all out and test with a quality tester. A cap test on a VOM is probably not adequate.

ESR increases as electrolytics age and increased ESR is never a good thing.

Electrolytic caps are rated for 1000 to 10000 hours @ maximum conditions. If operated at less than maximums, life can be doubled for every 10°C below max °C. Assuming 105°C caps and a 35°C internal temperature, that's between 125k and 1.2 million hours. Only a small percentage of the caps would be expected to have the upper limit. 1977 was more than a million hours ago, so a 40 year old amp is living on borrowed time.

If the ampzilla has never been recapped since 1977, as a technical type, I would never even turn it on without a full inspection and some critical level recapping

Ditto! 1977 is 40+ years and that's nearly 3 times as long as the recommended de-rated 15 years due to seal deterioration.

All capacitors dry out after awhile 15-20 years for sure 
Electrolytic power caps  for sure  . I owned a store and worked modding 
caps , there are several grades of quality  ,coupling caps,of various types like teflon, paper in oil.foils,  as well as  Electrolytic , including the top 4 pole cap types.  You get what you pay for  on average .

for the past 6 years i only use my equipment like 6 hours a week. should i worry about the 'caps'??

When it's time to change the power supply caps, your amp will let you know with a loss of bass definition soon followed by buzzing/humming. Until then, leave it alone if it works and there is no sign of physical damage.

And when it does so with a loud bang it is too late to save your expensive speakers.