Change the valve cover only when necessary, or any time a service requires removal of the top end and allows easy access and it makes economical sense to refresh it.
What you need at 70K depends on any service previously done. If no service records exist, I recommend the complete timing belt service usually required @ 60k.
Included Services & Procedures:
•Replace Air filter
•Replace Coolant
•Replace Engine oil & filter
•Replace Rear axle oil
•Replace Spark plugs (Valve cover issues here)
•Replace Timing belt (water pump and tensioner assy as well as cam seals, main seal)
•Rotate and Inspect tires
•Inspect Ball joints
•Inspect Brake hoses
•Inspect Disc brakes
•Inspect Drive belt(s)
•Inspect Driveshaft boots
•Inspect Drum brakes
•Inspect EVAP system (leaks)
•Inspect Exhaust system
•Inspect Fuel system (leaks)
•Inspect Steering link seals
•Inspect Transfer case oil
•Inspect transmission fluid & filter
•Inspect/Lubricate Grease fittings
•Inspect/Top Off Engine fluids