I don’t know what type of capacitors are used in Outlaw amplifier power supplies, but there is a known, slow deterioration of the dielectric in wet electrolytic capacitors when they spend long periods of time (read months) in a discharged state. Having the capacitor charged on a regular basis prevents this particular deterioration, it doesn't have to be continuously on. Conservative power supply design takes into account that capacitors will not always perform to their maximum capability and that some small current leakage and temperature build-up will occur. When the design allows for this, then the rated performance of the power supply will still be available even if some aging occurs. Basically, don’t worry, trust the very capable amplifier designers.

Stand-by versus total shut down: usually a stand-by mode allows a monitoring/switching circuit to remain normally powered while the rest of the unit is fully powered down. When a trigger voltage or command from a remote is received, then the rest of the unit is powered up. Usually the higher-power portion of the unit is fully shut down even in stand by, so, for these power circuits, there is no difference between being in ‘stand-by’ or having the unit fully shut off. Two questions: for regular use, do you want the unit to respond to an external command, or do you want to physically turn it on? If all users are going to be absent for many days, on a trip for instance, do you wish to physically disconnect your system from the electrical system and from any other external wiring, such as satellite, cable, or telephone lines, so that in the event of some freakish power event or lightning strike your system components are isolated (unless they are directly hit)?