The peak charging rate of the Battery may decrease slightly after a large number of DC Fast Charging sessions, such as those at Superchargers. To ensure maximum driving range and Battery safety, the Battery charge rate is decreased when the Battery is too cold, when the Battery’s charge is nearly full, and when the Battery conditions change with usage and age. These changes in the condition of the Battery are driven by battery physics and may increase the total Supercharging duration by a few minutes over time
I'm just conjecturing, but CHADEMO runs much slower than the Supercharger so it's probably not as bad/noticeable as compared to supercharging 150kWh/day everyday. Having said that, I'm not sure if it's worth a $400 CHADEMO adaptor unless you live in a condo/apartment and can't charge at home.
I agree with jcanoe... I'm not an expert, but I've only heard the factors that degrade battery life (maximum State of Charge) over time are: high temps (like battery preheating for supercharging), keeping the battery long term at very high or low State of Charge (%), and charging/discharging faster than 1C (1C is ~77kW for a model Y).
Bjorn Nyland had a good video on it here:
. His observation is that a majority DC-charged car had 6% max SoC degradation but a majority AC-charged car had 4%. But not exactly controlled variables nor a large sample size. The deciding factor in the video I think was probably high C + Supercharger preheating rather than DC vs AC.
For optimizing battery life on a model Y, 50kW on a CHAdeMO is probably the second best option for charging, only a 72kW Urban Supercharger is better. Free CHAdeMO are rare, I've only ever seen them on ElectrifyAmerica stations, where the $/mi ends up being close to gas. Use it! lol. Just charge only what you need to get to the next charger and a safety buffer, to keep near 50% SoC.