I get this code sometimes after the blazer's been idling for a minute or so. Is it a good idea to change these now? i know the code means check it out, but i acquired my blazer in june and i haven't changed them nor do i know how long the current ones been in. vehicle is at 146.5k.

P0147 indicates there is a malfunction in the heater circuit in the O2 sensor after the catalytic converter. That DTC means there is a problem in the circuit, not necessarily the sensor itself. It's always best to check and verify what the problem is before throwing parts at it. It might be just a poor connection or a broken wire.