SN74AUC1G66: Whether SN74AUC1G66 can work normally for a long time under 3.3V voltage

This is outside the recommended operating conditions, so the electrical characteristics or even correct operation are not guaranteed.

Just use the SN74LVC1G66.

Hello,

As Clemens notes here, the device is only rated up to 2.7V so going to 3.3V will not guarantee any operation or that the device will not be damaged. The SN74LVC1G66 has similar spec, is p2p to the AUC device and can go up to 3.3V so I'd recommend switching to that device as well.

Thanks,
Rami