Askcv
I would be very carefull about exceeding 250 based on the phraseology you have recieved. Controllers cannot authorize you to do(HOU being the exception). This is well established within the ATC community, not as well known outside. I have no doubt that was the phraseology you recieved, and it was probably the controllers desire that you do so. My guess is it provided him an operational advantage. Of course should anything happen, it would be denied. If a climb in excess of 250 was authorized/desired by ATC, the phraseology used wouldn't be cryptic.