Bad head gasket, how long can I drive it?

[koop]

As sort of a continuation of a prior post. Thermostat stuck, car overheated, replaced thermostat. My benz guy says drive it for a while and see what happens before pulling heads.

Well what is happening is that while the oil looks OK there is definetley water getting into the oil (I see no evidence of oil in water). Huge cloud of white smoke when I start it. Drives fine though. Doesn't overheat. I'm losing about an inch of coolant as measured in the resevoir every 200 miles.

I'm OK just filling the resivoir regurally but am worried about more substantial damage. Like hydrolocking the engine, scoring the cylinders, damaging rings ect.

What are my long term prospects here?

TIA