I am seeing a secnario where a signature that I generated with a
RSACryptoServiceProvider.SignData 90 days ago cannot be verified. Do
these signatures expire? If so is there a waay to turn that off?

TMK, an RSA key pair created with RSACryptoServiceProvider never expires.
Certs, on the other hand, build expire logic ontop of the RSA keys, but the
keys themselfs are just numbers/primes that do not expire.  I would say
something else is going on.  Post the code sample and the xml rsa key pair
if you want us to take a look.

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