[old_tv_nut]

If I recall correctly, the major manufacturers aimed for 10 years service at 2000 hours per year, with "normal" maintenance. Much of the passive component life depends on time and temperature. Higher rated capacitors and resistors would price a maker out of the market. Of course, competition for selling price prejudices component choice against considering total lifetime cost of operation/maintenance. Contrasted to this, the telephone monopoly expected equipment to last 25 years with essentially zero failures.

There's also a peculiar effect of component manufacturing tolerance. Carbon composition resistors cannot be manufactured to a tolerance of 5%, so 5% tolerance resistors have to be selected at the end of the process. This means that 10% resistors used by the smaller TV makers tend to be toward either the high or low end of the tolerance, so that individual TV sets are closer to drifting out of design tolerance as they age.

Big manufacturers like Zenith could get a reasonable price for the tighter tolerance components due to large volume purchases, while smaller makers like Motorola used 10% parts unless it was determined that it would result in too many rejects at the end of the production line.