To each his own. I find it illogical to double the cost of a head gasket job to avoid the possiblity of having problems in an area that never has problems. The chance of the new head gasket leaking within the next hundred k is about 100 times greater than the valves needing work in that time.
You can replace a head gasket a hundred times. You can not keep grinding valves and driving guides.
Bosch Master, ASE Master, L1
33 years MB technician