Oil in coolant reservoir?

I noticed oil in coolant reservoir so took it to mechanics and was told it was oil cooler seals. No overheating problems at this stage. I had them replaced with new seals but didn't fix the problem. Then told needed to replace oil cooler so had it replaced but still had oil in coolant. I was told it was residue and not to worry about it. Four times had it back to mechanic to fix this problem. I noticed it was losing a small amount of coolant as I had to keep topping up reservoir. Mentioned this to mechanic told keep an eye on it and top up as needed. Then I was driving one day not long after and lost power so pulled over immediately and there was no coolant in reservoir at all. It overheated. Found out later it was caused by a blown radiator hose, which caused a blown head gasket. Should the mechanic have checked hoses for deterioration at time of oil cooler repair? I have taken my car to this mechanics for the past 5 - 6 years and always had services done when due. This is the second time a faulty hose was not noticed and replaced and has caused major damage. Twelve months previous motor seized because hose let go, lost coolant and had to have the motor replaced. Cost $3,000.00. Is it the mechanics responsibility to check radiator hoses during a service and replace or at least notify me of the need to replace them? I have been without my car for 10 months now.