We have an EDM830 fitted and rarely to the CHT's, EGT and TIT get so hot that you can't lean in a climb. I lean using TIT and use that as my benchmark, and as long as TIT remains comfortable then CHT and EGT remain green and I'll lean in all phases of flight.
Actually with high altitude capable aeroplanes like ours which has a ceiling of 20,000, if you went full rich at high altitude during certain flight phases you'd likely have a rich cut and the engine would stop.....or you just wouldn't make your ceiling.