Lifespan of OLD (80's) electronics

I have a Sony stereo receiver/amp unit from circa 1988. I use it for all sound for my computer, PS3, and entertainment center. I am wondering about how the ways in which I use it might limit whatever lifespan it has left.

Currently it is sitting upright so that it has much more heatsink exposure than it is expected to have. The area it sits in has good airflow and is dusted regularly. The inside of the device appears to be nice and dust free. The unit, along with every device feeding it an audio signal, is hooked up to a UPS unit with voltage stabilizer to protect against surges and brownouts.

Given these conditions, I'm asking myself the age-old question: do I leave it on permanently, or turn it off when not in use? Part of me thinks that switching this device on and off is the most destructive thing I can possibly do to it at this point.

Any thoughts?