> "guaranteed to work for many years" if you don't need them calibrated I guess.
Unless you need traceability for contract or regulatory reasons, oscilloscopes don't need regular calibration. Most of the time, you're probably using them for rough visual confirmations (e.g. is this signal behaving like I expect it to) more than precise measurements. In any case, it's rare for an oscilloscope to go seriously out of whack without a physical insult (like being dropped or exposed to major overvoltage).
Unless you need traceability for contract or regulatory reasons, oscilloscopes don't need regular calibration. Most of the time, you're probably using them for rough visual confirmations (e.g. is this signal behaving like I expect it to) more than precise measurements. In any case, it's rare for an oscilloscope to go seriously out of whack without a physical insult (like being dropped or exposed to major overvoltage).