It's a statistical thing, which we might not like but that's how failure analyses works in aviation...
What is the chance of failure after a failure? Very remote that it will happen for the remainder of the flight. So Boeing will not tell you to "land asap" as it is not required. As a pilot you prefer to stay safe so nobody should oppose the decision to divert and land. Although there is no reason to rush, plenty of time to choose a suitable alternate for your company.
If you would end up getting an engine fire, the fire will eventually destroy the engine which will be visible in other ways. In that case you would consider it a land asap situation as you cannot confirm a possible fire to be extinguished.
It gets even trickier with cargo hold fire detection system failures in flight...
But as mentioned, get out the popcorn and shoot my opinion :-)