Expected Lifetime Mileage: Bottom Bracket and Headset I'll declare a personal interest in asking this question, relating to a dispute with a national UK bicycle retailer. I'm not looking for advise on how to resolve the dispute, nor for evidence / opinion to beat anyone with a stick. In fact, ultimately the sums of money involved are negligible, and almost certainly not worth my time pursuing, so please treat the question as "more out of interest"

Bike is a hybrid manufactured by a well known global bike company, 6 months old, less than 1500 miles. Predominantly commuter riding, road and pavement (25-30 mile round trip, two or three days a week). Whilst not a BSO, I do understand the OEM components to be considered "low end" quality. Weather - typical south west UK, and of my actual commuter days I have worked out the roads will have been damp or raining on roughly 20 days over the period since purchasing the bike new. So I would consider the use of the bike to be well within "normal" use and expected conditions.

My questions:


Would you be expecting to replace a low quality sealed cartridge square taper bottom bracket after less than 1500 miles riding in the conditions described above, and when making the decision on what to replace with, what would define a "quality" BB, other than relative price and brand?
As above, but this time consider headset / headset bearings.
Headsets often last the life of the bicycle. They can get "brinneled" or damaged in a crash or something, but 1500 miles is absurd. 

As for a bottom bracket, on the low end, maybe 5000 miles. The basic Shimano one most people use (UN51/55/similar) can reasonably expect 10k+ miles. But sometimes you get unlucky and get a bottom bracket that lasts maybe 500 miles. You may have just gotten a lemon.