I suspect the
actual washing action was not especially hard on the machines. The reciprocal agitation is, after all, hardly a new mechanical design.
It was the shift from agitation to spin, the enormous load of draining water and spinning (partially relieved by the neutral drain some models used) and the braking which, in my opinion, which caused wear and tear.
Partially because of patent limitations, partially because US companies did very little real new engineering, all those new programs of the 1950's had to be accommodated using the same, fixed stepper-cycle length of the original timers. There used to be lots of blank space on early dials where you turned and turned and nothing happened. By the time they had added delicate, permanent press, soak, second-rinse, etc. those 360° were being squared.
The washing action did vary tremendously, nothing comes even close to a thumper - I figure they were the only TL which ever really, truly came close to FLs in getting laundry clean. My rollermatic (the days she decided to work) could clean my grungiest jeans and T-shirts in one go; the turnover was just fantastic. And, if I recall rightly, the water consumption was not that bad, either.
Oh, well. Now that we have fuzzy logic controls, has anyone noticed their top-loader doing a better job of washing than the same brand did with the old mechanical "logic"?