As previously stated, you can run APRS on any amateur radio frequency where the emission type is allowed by the rules and the originating station has operating privileges. I've run APRS on 144.990 MHz for an event in a city center where I wanted to be able to hear our packets directly, but didn't want our packets to be clobbered by a high-profile digipeater in the city.
The problem with moving off of 144.390 MHz is that whatever digipeaters and I-gates that you might want to take advantage of won't hear your APRS packets. If you are OK with that, then have at it.
Bob Bruninga WB4APR used to talk about an hiking/running event where the checkpoints were in valleys and the digipeaters in the area couldn't hear the APRS packets coming from the checkpoints. So, they set up temporary digipeaters on ridge tops that listened on 144.990 MHz and transmitted on 144.390 MHz. These temporary digis could hear the checkpoints and retransmit their packets (remember, AX.25 digipeating is store-and-forward) so that other digipeaters and I-gates could hear them. Conveniently, 144.990 and 144.390 are 600 kHz apart which is a transmit frequency shift that most 2m radios understand.
Or, if you want your packets to not be relayed to the APRS-IS by the I-gates, you can append either NOGATE or RFONLY in your path. For example, a path of "WIDE2-1,WIDE1-1,NOGATE" will be heard and acted on by local digipeaters, but won't be sent to the APRS-IS by any I-gates in the area.
