He so often wrong about language, that any advice from Setanta might as well be dismissed.
The English is fine.
"The good things always keep on going, don't they?"
When to use this sentence??
When might this sentence be used?
In what situation could this sentence be used?
In what situation could you/one use this sentence?
First, you have to be clear on the meaning, Cathy. It could mean that the person has an optimistic sense, "good things continue" or it could mean that the person has a pessimistic sense, "good things end".
Why not try to create a simple scenario where you might use this line? Pretend you are a screenwriter.