Fast-charging daily: how much does it hurt battery health?

I keep hearing conflicting takes on DC fast charging. Some say it's fine as long as the battery is preconditioned and you stay under 80%. Others insist that frequent fast charging noticeably accelerates degradation, especially in hotter climates where thermal management has to work harder. My daily commute uses about 60% of the pack, so I often top up at a 350 kW station almost every day. I've owned my EV for roughly 18 months now, and I haven't seen obvious capacity loss, but the data on battery health from the car still feels like a black box. Has anyone run their own long-term experiment? Are there real-world log files or battery health reports from similar use patterns that show a clear difference between fast and slow charging? Curious what your service centers or onboard diagnostics tell you. I want to know if I should be reducing my reliance on DCFC or if the