There are certain people, like Chicken Little, that claim the sky is falling all the time.
They make these claims about crown rot, blaming other people, especially certain growers,
but never blaming their own atrocious growing methods.
If ALL your water lilies all die of crown rot, it doesn't happen all at once, or overnight.
If it happens, it means you haven't been very observant, and you haven't been growing them properly.
If you're out there every day pondside, you can spot it before it turns into a problem.
Tink, your chances of this happening to you are close to nil.
Don't let some old fogey make you believe that the sky is falling.
Besides, if this 'friend' knows this 'someone' who lost an entire collection to crown rot, ask them to back up what they say.
Ask them who it was, and how long it took.