synergy. An increase in the value of assets as a result of their combination. Expected synergy is the justification behind most business mergers. For example, General Motors purchased Electronic Data Systems in 1984 with the expectation that considerable synergy would result.
Filters can last from a few weeks to several years. In part, it depends on the materials they were made from, and their designed life span. As a general rule, most cartridge filters average 1 year. We recommend that you chemically clean your spa filters every 30 days to extend filter life. Not just spray them off with a hose, or rinse them off in the sink. A good Filter Cleaner & Degreaser will help remove oils and scum from the filter media.
Of course the answer is, it depends. Smaller signal tubes, such as the 6DJ8 are rated to last about 5,000 hours and the more durable versions will last incrementally longer. An output tube is typically thought to last 2,000 hours, but then you are talking about using them to drive speakers. When used in a headphone amp, such as the EL-34 in the ASL MG Head, the demands will not be so great, as when driving speakers, so they should last longer.