That old chestnut, comma usage.

I'm struggling with what I believe to be the most commonly misused punctuation mark in the English language, the comma. Consider the following sentence:

"They will have to do what you're doing, they'll have to work."

Is a comma okay here? From what I've read, one simple test is to ask if each part can stand on its own? In this case, it can, so I could, I think, go all the way to:

"They will have to do what you're doing. They'll have to work."

But this seems to trample over the fact that the two parts of the sentence are closely linked.

To me, a semi-colon feels wrong for reasons I'd have trouble articulating. So I am left with the single hyphen or the colon:

"They will have to do what you're doing - they'll have to work."

...or...

"They will have to do what you're doing: they'll have to work."

Both of these seem correct to me. I'm not fond of single hyphens because I invariably find myself over-using them. Same goes for colons, and the colon seems heavyweight for casual use.

So, back to my original question: is a comma okay in my example sentence?

Any advice or opinions would be gratefully received.

Kind wishes ~ Patrick