I don’t know if Clint Eastwood ever actually said this. When I saw it I thought “that’s right!”. There are no guarantees in genealogy. Or in life!
I am often asked “if I do ______ will it give me the information I need?” and the answer is always “I don’t know”. It might, or it might not. There are no guarantees in genealogy.
The toaster will come with a guarantee for a specified period. A subscription to Ancestry or FindMyPast or any other paid website will not. Nor will membership in a family history society. Nor a book you are tempted to buy. Nor a CD.
The record with the information you are looking for may be in there, or it may not. It may exist, or not. It may exist but not in the form/place/date you expect.
Even if it’s not there, that is information you can use as well. Think about the possible reasons that it would not be there.
The only guarantee I can give you is that if you don’t try anything new you won’t find anything new.