Negative Feedback and life cycle of Vacuum tubes
Voltage negative feedback with valve amplifier is here mostly to enhance the bandwidth, reduce distorsion and the output impedance. If this is desirable in the hifi world, it has less important in a guitar amplifier where distorsion is wanted and 50Hz-15kHz is common bandwidth. Furthermore, if on the paper negative feedback has only advantages exchanging gain for stability, in the reality, it kills spontaneousness this is why it is often presented as an option in a guitar amplifier.

So no, negative feedback has nothing to do with valve serviceable life. Heater voltage and respect of the DS values are by far more important.