Haaaaaaaaaaaaaaaa hahahahahahahahaha!!!!! Hiccups for a year... I had that once
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Now where were we? Oh right, I don't want to freak anyone out... just add a little color to the discussion.
Roundworm larvae make migrations and actually bore through different organs, damaging them in the process. They have a direct life cycle and can build up to dangerous levels without treatment. This probably isn't what we're dealing with since the "clicking" is sporadic, and the snake has been this way for so long.
Lungworms affect respiration, but they cause gaping of the mouth, secretion of an exudate, and persistent noise. They weaken snakes and make them vulnerable to bacterial infections. Again, not what we're dealing with due to the lack of certain symptoms and extreme persistence (6-7 years).
A bacterial infection, such as pneumonia, could cause similar symptoms, but it would have had its way with the snake long before now.
It sounds much more like an agitated snake. Some shake their tail. Some flatten their heads; some bluff strike; some bite; others click when they're feeling irritable. I wouldn't sweat it, but I know how unnerving it can be when something doesn't seem quite right with a snake that you've had for so long.