The response from the agent didn't mention anything about it being too long ago, simply that they don't do it.
I responded saying that I could have stomached an answer that it had been too long, but to use the excuse that offers change is contrary to the extremely frequent bump they've dozens (or more) of other cardholders.
"Let me explain, when you apply for a new card, there are
various sign up deals offered to new cardmembers. These
offers change from time to time.
As much as I would like to help you, I regret to inform
you that I am unable to honor your request for the sign up
bonus offer of 30,000 reward points on your account, since
these offers are only available to new applicants. I
apologize for the inconvenience this may cause."