Cap life span?

If you look at the datasheets of aluminum electrolytic caps; you'll find that their expected life spans are noted in hours, at a certain temperature. Some datasheets even list an expected shelf-life. These sites each mention different ways caps age/lose their values: ( http://www.elna.co.jp/en/capacitor/alumi/trust/index.html ) ( http://chemi-con.com/u7002/life.php ) Some good info here: ( http://www.hans-egebo.dk/Tutorial/electrolytic_capacitors.htm ) If the amp is approaching the 20 year mark: A cap change is a good preventive maintenance measure, and you'll probably notice improved performance in the system's bass & overall dynamics.

I guess I've replaced WAY too many electrolytics, in power amps, Leslies, Tubed Organs and speaker systems, pro and home(for myself as well as customers), to buy into some the above statements.

Although Tantalum caps are considered, "electrolytic"; there is no liquid electrolyte(totally different construction) to dry out, or expand and blow out the vent. Two major reasons for electrolytic failure. Solid polymer(ie: PEDOT) electrolytics are another excellent option, if applicable. Try finding either, in a value usable for a power amp PS filter cap though. I've installed Sanyo OS-CONs in my TACT preamp's PS, with excellent results.