I see, so the lack of lubrication is what destroys the fan.
Now, I've read about fans that use a sleeve bearing, but they are "sealed". That means there is no outlet for the oil. Does that mean they can't leak?
I've read about the Cooler Master Sickleflow and someone commented that "it is sealed behind a hard plastic plug, so “long life” may simply mean that it can’t leak." This is from a fan roundup done with the NH-D14. I wonder if the Sickleflow is one of these leak-proof fans.
They are all listed as "long life" its a marketing term, get use to them. Sleeve bearings do not fair well when mounted horizontal because of the wearing surface, you should google some images of plain aka sleeve bearings, when mounted right, the weight of the shaft will be on the correct wearing face of the bearing, when mounted horizontal however, this is not the case and can cause uneven wear or wearing on the outer edge of the bearing which can lead to extra noise, grinding or ticking, often because of much greater shaft play from the odd wear. It has nothing to do with oil leaking.
Also, the R4 fans are crap, get something better, there are many MANY choices out there that perform better and sound better.
Sleeve bearings use grease. All sleeve bearing fans have hard plastic button under the label.
When a sleeve bearing jams after a few years, that's where I go and clean out the old grease and replace with fresh one.
Sleeve bearing should not be mounted horizontally as the weight of the fan on one side creates a torsional force along the axis of the shaft. If mounted vertically, the shaft is positioned nicely in the center of the bearing.