Our boiler is only 3 years old but we have had problems with it ever since it was installed. We have just had work done to repair the floor after it leaked and it was supposed to be fixed but it's still losing pressure. I'm going to complain to the manufacturer!
Your boiler should be covered under warranty, so I would definitely call the manufacturer. 3 years is a ridiculous amount of time to be having an issue with a boiler. Most of them have, at the very least, 5 year warranties. Good luck!
Boiler problems! 
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