On average, wheel bearings can operate for up to 70,000-100,000 km. Yet, their actual operational life depends on a number of factors, among which are the following:
driving manner;
average speed when driving within a city or along highways;
road surface quality;
design of the specific wheel bearing;
condition of sealing components and other suspension parts;
mounting place: rear wheel bearings can operate a bit longer if compared to front wheel bearings;
mechanical load upon a hub: a wheel bearing premature wear is caused, as a rule, by installing spacers, as well as by using heavy-weight brake discs and tyres.
If any subtle signs of a bearing assembly malfunction are detected, perform an urgent diagnostics and replace a spare part if needed.