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In a well-designed circuit, only about 2/3 to 3/4 of rated working voltage is actually applied across any electrolytic capacitor. With re-forming to the stated maximum leakage specification, actual operating DC leakage current will be far below maximum permissible. I have had excellent results, even with equipment which is kept in the less than ideal environment of my basement workshop. Variations in temperature and humidity are the main reason my 547 requires maintenance every 3 years and why I perform maintenance at 2 year intervals.
I provide additional overload protection to prevent marginal performance from becoming catastrophic chain-reactions, and I've seen far more cases where catastrophic failures resulted from well-meaning attempts to re-engineer component layouts to make components which did not meet one or more of the original selection criteria of the original part fit than from any other cause. As stated, though, I am working toward a solution to the shortcomings of restuffing cans. I have, however, had very good results with properly tested and re-formed original and/or NOS units. Being bitten by an unexpectedly "live" can often results in accidental damage to internal components due to involuntary recoil from the shock. This is yet another reason why I minimize re-engineering. I suppose a reasonable compromise when re-engineering would be to wrap all exposed cans with a single thickness of PVC tape to minimize shock hazard from a "floating" can.
I've worked on sets where a recoil from a shock had snapped tuning slugs and/or toppled and destroyed IF transformers. The all-time worst case of "permanent display piece" I have ever seen was, unfortunately, a very rare early color chassis whose owner had re-engineered one too many stages in the process of recapping (flyback toasted, IF transformers wrecked, severe instability in the few circuits that hadn't cooked). Failure to do a basic preliminary inspection is another catastrophe waiting to happen, as another unfortunate customer's listening test on a just-acquired vintage stereo receiver ended with a small fire under the power transformer, preventable had he merely checked to make sure that the fuseholder on the rear panel had not been bypassed before powering up. That unit was eventually restored to working order, but not without a costly transformer transplant.
Not at all advocating the careless handling of "unobtainium" here, merely pointing out that selection criteria other than just capacitance, working voltage, and leakage current are involved and there are potential trade-offs involved in re-engineering which require some careful consideration. Your mileage may vary.
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