The first point has an obvious response and the last is speculative.

I find interesting to address the middle one statistically.

A given machine has a number of random events that can kill it. Each possible event type i can be modeled as a Poisson process Xᵢ with, in a given year, probability λᵢ. The machine survives in a given year if no occurrence of event i happens, with probability Pr(Xᵢ = 0) = exp(-λᵢ).

For instance, a device with an average lifetime of 8 years and a single possible cause of death, has λ = -ln(½^⅛) = 0.087.

Given N independent event types (say, if you have on the order of N components), the yearly survival of the overall machine has probability Πᷡᵢ exp(-λᵢ).

Thus the lifetime of the overall machine is ln(½)÷ln(½^(Σᷡᵢ 1÷Lᵢ)) = 1 ÷ Σᷡᵢ (1÷Lᵢ) if each component has lifetime Lᵢ.

For instance, two components with an average lifetime of 8 years yield a single machine with an average lifetime of 4 years.

The more death-causing event types there are, the smaller the lifetime; and a general-purpose robot inherently has more.

I believe this result is counter-intuitive, and is the reason you might be led to think I am overly pessimistic.

Engineers take this phenomenon into consideration and design systems with redundancy and/or easily replaceable parts. You need specific numbers for the design in order to treat this mathematically.

> ... machine ... has ... events that can kill it ...

> ... N independent event types ...

So if the robot blows a $0.03 (i.e., 3 cents) electrolytic cap [0], that's an independent event type that "killed" the machine? Just trying to get a sense of how you define "machine kill" (and as I said I mentioned a big caveat of right-to-repair laws).

[0] http://amzn.com/B01MSQOX0Q

Sorry, what is the supposedly obvious response to the first point?

Why does your argument not show that cars would have a similar lifetime?

It shows that cars can never reach the pricepoint of a bike for the same lifetime, because the increased number of failure points require an increased level of quality of each part to yield the same lifetime.

stuff goes wrong with cars all the time. most of it isn't critical to the core function of the machine. cars also undergo routine maintenance where parts are (hopefully) replaced before they fail entirely.