1. For the general case - I think that the best way to decide if you need to increase resources is to see if current settings satisfies your operations.
Thumb rules for logging:
a. Can log server handle all the logs sent from all the gateways - if gateways have local logging due to log server resources it's a good sign to increase. In general I also recommend to activate log forwarding if not defined already.
b. If the speed of response satisfies you.
c. If you want to increase log retention (storage)
3. Not only do I recommend to do so, E1000 will be blocked on future versions. The reason is that is EOL from security updates so from security POV it's important.
Kind regards, Amir Senn