how to plumbing: How long until a leaky toilet rots the subfloor?

I think it’s been leaking for about a week. The carpet in front of the toilet (where your feet would be when you’re sitting) has small wet spots. I’ll repair the leak, but how do I know if the subfloor is rotted without pulling up the vinyl floor covering? The floor is peel-and-stick vinyl squares and the wet spots on the carpet are exactly over the “cracks” between the vinyl squares.