Isn't it ironic...

[Suff]

Joints in use regularly stay moistened but if they are out of use for a while they dry and crack. Also drains left for a long time tend to dry and harden anything which is already in them. Once they have hardened they become an obstruction which traps more and more crud until they block.

It's like the person who drives their car ultra gently over bumps because their seals on the dampers might go. All they do is build up a hard shell of crud on the damper rod and the one day they are driven through a pothole the crud rips the seals to bits...

Things which are used with normal frequency tend to stay working. Conversely things which are pushed to their limit tend to fail more often than not because their build quality is governed by the middle point and not the limits.

Sorry boring off topic digression. But it's morning and I'm trying to get my head into work mode.