OpenVPN's approach is to have every config key imply a valid config file entry and a long-arg. So if you see the line `tun-mtu 1500` in a config file, you know

OpenVPN's approach is to have every config key imply a valid config file entry and a long-arg. So if you see the line `tun-mtu 1500` in a config file, you know you could use the arg `--tun-mtu 1500` on the command line, and vice versa; if you see somebody use the CLI arg `--proto udp` you know you could put the line in your config file `proto udp`. I think mysqld has a similar approach, though I don't think it's as complete. I'll bet both of those projects would answer that there's no such thing as a tipping point where you tell users to use a config file. They're just two ways of doing the same thing; use whichever makes sense for your deployment.