P38 diesel valve stem seals

I am cleaning up a head to go on mine later this month, should I strip it down and replace the valve stem seals as a matter of course? I was thinking they should last many more miles but the head is off and I have some time to do it.
It had done about 150K miles, looking at the rave I need a protector to slide over the valve stem on fitting are these available or any good tips for fitting them? Murray.

Decarbonise the inlet and exhaust tracts, seat the valves as required, fit new seals. Use the fitting caps for the seals or you will destroy them when you insert the valves. Once fitted the valves must not be removed. Seals should come with valve insertion caps.