Very easy to forget about and can cause a really horrid accident as the bearings will seize and the dog bone snaps turning your bike into a chopper. Not good at speed.
The bearings in the dog bone and triangle are subjected to a lot of water and rubbish from the road. the bearing seals don't do good enough a job to keep them clean. they have a habit of seizing. Also, the bolt holding the shock to the triangle has a habit of seizing.
Therefore greasing at every yearly service using waterproof (marine) grease is essential.
Here is the tale on the forum and also the sizes of what is required if you are wanting to buy.
Even with yearly regreasing, I would say they are in a bad state after 5 years and should be replaced which is easy enough.