Which guidelines should I trust choosing crystal for oscillator: AN4488 or AN2867?

[RDien]

AN4488 goes like:

Why 15 pF is a maximum value? It came out of nowhere.

At the same time AN2867:

Emmmm...

So I am confused. What should I do now? Never use 12.5 pF crystal or use it and do the calculations in accordance with AN2867 to get accurate values?

[TDK]

I would duplicate what is done on known good ST hardware.

[RDien]

Thanks! That is exactly what I am doing right now! But this is not my case, because what I need is a device working reliably 24/7, 365 days per year in a pretty harsh environment. It is power supply powered, so the power consumption of the RTC oscillator with 12.5 pF capacitors is the last thing I'd worry about. Unfortunately ST hardware I can reach is not designed at this level of robustness.