All depends on your self service skills, if you don't mind getting your hands dirty, then my personal routine is as follows. (each cook has his own recipe) Once a year I'll do a full strip of the bike and check all bearings, in pivots, headset etc. If bearings are turning freely with no grinding or play, will leave be till next check. With wheel hubs. Shimano - Cup & Cone, those should be cleaned and re-greased every 3-4 months or so, get the LBS to teach you before trying yourself. If sealed bearings I would check each individual bearing on the once a year check. With consumables, (chain, cassette etc) that all depends on the conditions you ride in, if you like to ride in the mud or dry dusty conditions then you'll need to change the chain more often, like that you can keep using the same cassette for at least 2-3 chains. Lastly a pressure spray as convenient as it is, does generally not go well with bearings especially if you spray directly at pivots, BB, headset etc. The water can get passed seals and into bearings If any bearings are creaking, stiff or do not turn freely then they should be checked and most likely replaced.