PPP Issue with Mac OS X--Stable Connections

We just returned from a trip where we used our Pismo's internal modem with Mac OS X's PPP dial up (the Internet Connect application) for the first time to get on the internet. Previously, we had only used OS X to connect to the internet via a cable modem or a local area ethernet network. The internal modem is configured in the Network system preference panel under the TCP, PPP and Modem tabs. One change we made to the default values was to uncheck "Use TCP header compression" under the "PPP Options" button on the PPP tab. We did so for stability on the recommendation of numerous posts to the X4U List. Our numerous hotel room telephone connections over two days lasted as long as two hours and we never had a dropped connection.