A stiff link is caused by a damaged O-ring (or X-Z ring)
The captured grease escapes and moisture enters, rust is developing and causing the stiff link.
A brownish deposit can sometimes be seen on the sideplates too.
The chain needs to be replaced.
Premature wear of O-rings can be caused by brushing or even by chain wax capturing dust and dirt, acting like an abrasive.
A chain oiler is the solution, it will keep the O-rings healthy and the chain lubricated.
I am a big fan of Pro-Oiler chain lube systems, because they lubricate automatically depending on speed.
So at a traffic light: no lubrication at all, and the faster you go, the more oil...
That's why it is very economical with oil too, it uses just 100ml. every 3000 miles. (better for the environment too than using spray cans)
The speed is monitored by an integrated GPS module. (or you can buy the cheaper versions with a reed switch and magnet)
In the rain you can boost lubrication while you are riding.
(check out my post on installation on my Empulse R)With the oiler I managed about 60K miles on a single chain on previous bikes.
Before that, using chain wax, it was just 12-16K miles.
There's also a lot of difference in quality between chain brands too, I prefer DID and RK chains.