It is not a question of volatility or curing time of some silicone sealants that leads to O2 sensor failure.
From a tech course manual from a major car manufacturer (which is copyrighted and which I don’t have permission to copy):
“When silicone burns in the combustion chamber, it causes a silicon dioxide glaze to form on the oxygen sensor. This glaze causes the sensor to become sluggish when switching from rich to lean, and in some cases, increases the sensor minimum voltage on the lean switch. This causes the fuel system to spend excessive time delivering a lean mixture.”
The SiO₂ deposits on the sensor are either a white glaze or a light gray dust, quite distinctive from other deposits that cause O2 sensor failure.
This outgassing of SiO₂ particles continues long after the sealant has cured, and occurs whenever high temperatures are present.