I normally cruise at 2400-2500rpm so I guess I can lean the mixture at will?
I'd be careful with that.
When I had too much time on my hands a while back I delved into the performance graphs and produced a table for the sake of having a reference by which I can quickly determine whether or not it is safe to lean the mixture. The essence of the table is that by checking RPM against pressure altitude I am presented with the OAT value that corresponds to 75% power; if the actual OAT is warmer than the presented value then it is safe to lean the mixture.
What struck me about the data is that although it seems that you are generally producing less than 75% power at typical cruising RPMs and at typical temperatures from 1000' PA and above a 50RPM increase necessitates an increase in OAT of 15 degress celsius if it is to remain safe to lean the mixture. We all know how easy it is to inadvertantly gain 50rpm with a fixed-pitch propeller, especially when it's turbulent.