kamenko,

With sleeve type bearings, clean / cool water is the key to long life, whether the bearing is bronze, rubber or other.  I have seen rubber bearings in deep well pumps that were operating for over 20 years, and they were still in good condition.  The reason the pumps were removed was because the bowls (C.I.) were badly corroded.  If you are pumping some sand or abrasives, the life is reduced accordingly.  However, rubber bearings are also good in applications with small quantities of sand, because they will pass sand particles through without cutting the rubber.  Pump manufacturers will provide maximum recommended sand content for reasonable bearing life.  Rubber bearings are not particularly good for application in liquids with high density, sharp edge solids content.  This type of solid tends to cut the rubber resulting in reduced life.

Unlike anti-friction bearings, sleeve bearings do not have an estimated life span.  This is because they operate by establishing a fluid film (hydrodynamic wedge) between the bearing and shaft sleeve.  Therefore there is no contact between the bearing and the sleeve.  As long as the fluid film is retained, the bearing will last indefinately.  This is not the case with an anti-friction bearing which has a definite life span (based on load conditions), which is provided by the bearing manufacurer.