Fuji,
I developed the following rules for my self when I rented that IMHO would give me the best fuel economy, and do no damage to the engine.
If the aircraft you fly:
1. Does not have effective temperature monitoring eqpt.
2. Does not have a wobbly prop.
3. Does not have fuel injection.
Following initial climb out reduce rpm’s to 23-2400, then lean until the engine runs rough, then enrich until it runs smoothly.
Do this each time you change the throttle setting, or attitude.
In the initial climb stay full rich.
In cruise climb lean above 3000ft.
Given 1, 2 & 3 above, it is unlikely the engine will run at or above 75% power in a leaned condition.
To paraphrase Deakin , with power settings below 75% whatever you do with the mixture control will not hurt the engine.
Regards,
White Bear.
Edited to add that I also leaned aggressively on the ground prior to departure and immediately following arrival.