I had trouble accepting 65Degc for my Rasp4 with the Dac plus Adc.
I bought a spacer and created a bit of space between the Hifiberry board and the CPU. I bought a cheap Acryl base and mounted extra spacers. Then I mounted a small fan suspended by strings on the small side blowing onto the cpu. I took the power from the doubled Gpio being present on the HB board. Temperature is down to 45Degc. The Raspi4 might tolerate 65C, but it does for sure age faster at that temperature.