2004 Honda Civic Head Gasket/Heater Problem

david yankee

Hi Scotty. Hope everything is well for you.
I have a 2004 Honda civic with 215,322 miles. The engine head gasket had been blown twice at 107k miles (year 2009) and 176k miles (year 2016). Both times, the combustion exhaust leaked into the cooling system.
It had been 4 years since the head gasket was replaced and resurfaced along with valve job, new radiator hoses, new heater hoses, new coolant, new water pump, and OEM thermostat. The radiator had never been replaced.

Recently, the heater began to blow cold air even at the hottest setting after 15 minutes of driving.
The engine coolant temperature went up from 183F to 204F as the heater start to blow cold air. As I accelerated after stopping from the traffic light, engine coolant temperature sometimes went down while the heater temperature returns to normal.
Sometimes, hot air is return after the car accelerates. Sometimes, there are no hot air from the heater.

Before the heater temperature problem, engine coolant temperature never went above 183F with the heater on.
There are minor oily stuff on coolant. The reservoir bottle had been getting dirty and dark grey noticeably over the last six months.

A mechanic performed an Engine compression test. The result is okay. Cooling system holding pressure.

Is it worth doing cooling system repair for this car such as replacing the radiator or the water pump this time around at 215k miles?
Could the engine head gasket be leaking or blown?

How long (how many miles) does a typical head gasket job last? Thanks a million for your expertise and help. Take care.