After your reference flight, you can start adjusting the motor timing in small steps.
Change the timing by 1 degree at a time, then repeat a comparable flight and check the results. Compare motor temperature, ESC temperature, telemetry values, flight time, and the way the model feels in the air.
Try to look for a trend, not just a single number. One flight can always be affected by wind, flying style, battery condition, or how hard you pushed the model. Several comparable flights will tell you much more.
In most cases, you want to run the lowest timing that still gives you all the power you need. This will usually also be the setting that gives you the best efficiency and the longest flight time.
A good method is to lower the timing step by step until you notice the first slight drawback in power or smoothness. Then go back up by 1 degree and leave it there.
That is usually where the motor is happiest — and happy motors tend to make happy pilots.