yeah I do agree that the K series is not the best when it comes to head gaskets, though the actually didn't mention that it was a k series engine at all, it could be a M series, a T series,a S series or even a honda engine in a 200 (though at 36K a k series is most likely)
there is no set time for them to go, I had a 200 k series, the head went at 40000, I have had a montego in the past the head went at 68000. I had a rover 820 and the head did not go at all!
The best thing to do is make sure that the cooling fan on the radiator comes on when the engine starts to get hotter i.e. when stuck in a traffic jam.
A common failure is the heat sensor switch that turns this fan on, it's usually attached to the radiator somewhere by a screw on nut and is a cylindrical object with two wires coming out of it.
A way to test this is working is run the engine with it unscrewed from the radiator.
Dip the end of the 'switch' in a jug of boiling water, if the fan comes on the switch is ok, if not get it changed.
my wife had a 200 ..honda engine...the head gasket blew at 45000..but because the honda engine is all alloy then it was not just the head that warped but the block as well..so was totally uneconomical to repair
most rovers and especially freelanders are famous for head gaskets going