It's not instantaneous; it happens gradually over several incidents. Each time you apply non-silver, the percentage in solution goes down. The less silver in solution, the faster it dissolves out of the contacts. There's not much there to start with, so it doesn't take a lot of abuse to kill it.
I have not ruined any myself, but I had to remediate some in a scope I acquired.
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of David DiGiacomo <email@example.com>
Sent: Thursday, January 24, 2019 2:10 PM
Subject: Re: [TekScopes] Tektronix 575 help
Do NOT use non-lead silver bearing solder on the ceramic terminal stripsThis seems farfetched to me. It seems like it would only be a problem
if you managed to remove all of the original solder, and repeatedly
resoldered with tin-lead.
Has anyone ever managed to remove the silver plating from a terminal
strip, either in the course of normal repairs, or by intentionally
trying to do so?