Just run lncli feereport
If your are not moving the amounts in your channels that should indicate how much you have earned.
But at this time people have channels with subsatoshis or zero fees. I have had my nodes running for 3 months and no one has routed through me (or not that I know of).
If there is a better solution like a line on the logs, please tell me
Checked. All my fee sums are zero.
Do you suppose routing fees might increase as larger hubs come into existence? My reasoning is that those who have larger funded channels will be able to service more users, which will lead to them being able to dictate higher routing fees for the sake of convenience (so users don't have to create new channels for larger sums, for instance).