I've been mulling this over, and want to add another comment.

+ Manufacturers generally wish to expand the number of events and conditions which void their warranty, as long as they can do so without looking like they are weaseling out of THEIR obligations. Thus, in the pool industry, it's common for "high chlorine" to void warranties, even for products not affected by chlorine.

+ However, rubber materials ARE affected by chlorine, and rubber materials suitable for high chlorine environments (such as pools) tend to be at least a little more expensive than ones not suited. This fact is, I believe, behind the poor performance of so many non-OEM rubber or elastic replacement parts.

+ I have frequently published, both here and at PoolSolutions, my recommendation that pool owners NOT purchase generic elastic replacement parts, but instead seek OEM parts.

+ Pump seals usually consist of 5 parts: a ceramic seal (which may have an elastic gasket or O-ring), a machined carbon slip ring, a stainless steel washer which holds the carbon, a stainless spring which keeps the slip ring tight against the ceramic, and a rubber boot and seal which makes a watertight connection against the pump shaft.

+ It's quite likely that non-OEM seals may use low-grade elastomerics, which have poor resistance against chlorine, for the boot and seal. Such a boot can fail due to NORMAL levels of chlorine.

+ If your pool guy used trichlor tabs in the skimmer AND your pool had a pump timer, then your seal would periodically get 'hot shots' of very HIGH chlorine levels due to the slug of very highly chlorinated skimmer water that would circulate when the pump first came back on.

I know this just adds to the complexity of the situation, but these are all factors the likely do apply to your situation.