People are right to worry about the phone's battery. If you want to keep it that long, get a 500mA charger and slow charge it every night and avoid deep discharge.
Charging above a certain speed, does degrade the battery faster. Thinking that by slow charging your battery will last any noticeable time longer is where this all falls apart.
Right, which is why the Pixel still charges slow af(25W). It's really because it's a single cell battery, the phones with really high charge speeds are multi cell arrays. Each cell can be individually charged at similar wattage to the pixel but with a much smaller cell size it appears to charge faster. I think the OnePlus is the one that is advertised to charge ridiculously fast, iirc it is a 4 cell array, which is why it can charge at 100W (25W per cell). Technically the same speed as the pixel but you're simply charging 4 smaller batteries at once.
The charge speed to degradation is actually based on the battery capacity. Single cell vs multi cell won't make a difference there. That has to do more with the way the charger is setup.