[bumby]

Depends on what you mean.

I’d like to be at or near the first flight of a new plane using a time-tested design.

Failure rates (more specifically hazard rates) in most components tend to increase with time (I.e., follow a time-dependent failure model like a Weibull distribution and not a constant rate model). The “bathtub” curve is usually more associated with components with a constant failure rate (where the ideal place is after infant mortality but before wear out).

There are two types of uncertainties here and I think we’re talking about different ones. One is a design uncertainty that can be mitigated using a well-used and understood design. The other is a component failure uncertainty which increases as service life increases. So the ideal place to be is in a well-vetted design with new-ish components.

[nickik]

I not arguing about design uncertainty, rather production uncertainty. A failure in the production is more likely to fail on the first flight then the 3rd.