You don't say why you have had to have them done again, was the pump leaking, did the alternator fail, etc ? It's most unlikely that all the same items would fail again all at the same time! It may also be that they have probably fitted the cheapest(& poorest quality) parts they can get, & you have to question if they were replaced at all in the first place, the cambelt & tensioner & water pump are not easy to see without removing the plastic covers!
jim
September 2010