You should use different keypairs per identity, and different secrets per service. However, when a service relies on public-key cryptography, there's no reason

You should use different keypairs per identity, and different secrets per service. However, when a service relies on public-key cryptography, there's no reason not to reuse the same keypair for different services. If your private keys are stored on your local machine, chances are if one is compromised, all are compromised.