.Land line phone goes dead every so often, every phone in the house does the same.

I want to know why my land line just goes dead every so often, we have both digital and basic cordless phones, they all go out not just one. Its happened ever since we have lived here almost eight years. called support but to be honest never got anywhere, they say unplug, do this and that but it never helps. They just go dead then maybe five to ten minutes later they are alive again, its weird. If you call it the tone will ring in your ear but the home phone won't because its dead.

So I know its not the actual phones or there leads as it wouldn't make them all go out so t must be something else.

Any intelligent suggestions would be appreciated