Q: How often are you suppose to replace a new throttle sensor ?

The throttle position sensor (TPS) is only replaced if it tests bad. So there is no fixed replacement interval or "lifetime" for that part. They do occasionally fail though, in which case the Check Engine Light will illuminate with specific TPS codes.

Although a faulty TPS could account for the symptom you are describing, there are other causes as well that a mechanic would check. Once the TPS is tested (they are testable), and it tests good but is still accompanied you are having shifting problems with the transmission, that could reflect a fault in the transmission, such as the valve body and/or shift solenoids. You might also have companion issues, such as a plugged transmission filter causing inadequate or unstable hydraulic pressure. By the way, valve body problems in the transmission do not necessarily mean you need a new transmission and such problems can often be repaired on the car (without removing the transmission). If you need a diagnosis, a certified professional, like one from YourMechanic, can diagnose the loss of power symptom and jerking issue in order to have this resolved properly.