IMO A bit too much of a nuisance to replace the heater control valve just for the heck of it. Maybe every time you change the coolant, and definitely when you replace the water pump, it's a good idea to carefully inspect the whole cooling system while it's drained, checking for any damaged, crazing or gummy rubber hoses, pinching them and stress testing them with movement, also stress testing the heater valve by trying to break off the nipples by hand. If everything survives that then it's going to last a few more years. The original metal and bakelite style of valve is the only one known for sudden failure.

Similar to Randy, I handled an original heater valve while disconnecting the hose to replace the heater core and the nipple just cracked off, saving us from a later emergency guaranteed to happen at the most inconvenient time. I'd known they were a problem area, just never bothered to check this one. As another cooling system story not that many years ago in one of our 940s, on a long highway trip and over an hour drive from home, I had what turned out to be a head gasket start to go that under the added pressure split open the sharp bend in the lower heater valve hose sending the temp needle into the red. I bummed a couple of milk jugs full of water and turned around to drive home, mostly taking secondary roads, stopping every 10 mins or so to top up. These red blocks can take a lot of abuse. An old saying from the Amazon days was "Don't be afraid to drive 'em like you hate 'em", and we said that half-seriously knowing full well that we were challenging the Norse gods.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now