Amplifier Longevity Question

Generally electronics should last a good 20-30 years of moderate to regular use before its capacitors and other electronic components do not perform as well as they should. Given that you haven’t used them that heavily, you should probably expect them to work well for another 5-10 years. 

Because of their age, it might be a good idea for a tech to look them over to make sure they are running to spec. Amplifiers tend to need bias adjustments over time, and sometimes this can make the unit sound better on top of lasting longer. 

Assuming one maintains amps with periodic replacement of parts and keeping in spec they may have great life expectancy, especially those with point to point wiring.

@blisshifi You mention 20-30 years plus the extra 5-10 years with proper maintenance. What would be cause of failure past this time? Are you thinking of things like circuit boards, transformers?

The two big components that are at risk of ending a piece of gear are output transistors or tubes and capacitors.

Power supply / bypass capacitors may leak over time and need to be replaced.  I put the longevity of newer caps around 30-40 years.  Sometimes those fail catastrophically and take out mulitple parts at once making it financially difficult to fix.

The other part to this is whether the output components are available if they fail.  Many a great receiver and amp have died from using parts that were no longer manufactured.

+1 @erik_squires

And I would say not just output transistors but any transistors. If an amp drifts out of spec, or if it is a Class A or AB amp and that constantly generates a lot of heat, the transistors can get exhausted and not perform their switching duties, fail and cause leakages or shortages that can send the amp to protection more or fry them.

Tantalum capacitors almost easily fail and can melt or bubble up with too much heat over time. Electrolytic capacitors typically don’t leak, but they just don’t store and deliver to their spec as they dry up, which starts to introduce distortion and/or thinness to the sound.

Transformers are generally incredibly durable and very difficult to ruin unless too much excess current fries a fuse that is built into it. And circuit boards are generally fine unless something causes a short to fry it, typically from one of the electrical components as described above. 

@blisshifi

You aren’t wrong, it has just been my experience that the output transistors are the one’s that are most likely to go out of fashion and impossible to find replacements for.

The small power transistors tend to be interchangeable or remain in production forever.

To answer the OP's question I was answering the question of"when will my gear die and not be fixable?" vs. how often will it need to be serviced.