Coolant loss overnight

[Guest]

Hi,

My car is:
1998 S70 T5 Auto (1997 in-service date)
180,000 miles

My car was parked over the weekend. When I parked it, I checked the coolant: It was at minimum. After the weekend, I checked it before going to work. There was no coolant in the tank. I couldn't locate trace of coolant on the tarmac since there was a layer of snow under the car. The indep. garage dealing in saab and volvo say that the head gasket is leaking. They backed it up by saying they found white powder in the exhaust piping leading to the turbo. They said that this is the initial stage of a gasket failure

I am skeptical that head gasket fails at this mileage and expect that it should have 30,000 miles more to go.

I have 180,000 miles (260,000km).

Can you tell me if this sounds right?

Thanks.