Just use a single SSH key per device, any more than that is redundant. If someone hacks your machine and a key is compromised, then all keys are compromised any

Just use a single SSH key per device, any more than that is redundant. If someone hacks your machine and a key is compromised, then all keys are compromised anyway... it does mean if one of your github accounts is hacked, then all your keys are compromised, it's a tradeoff on security...