If you search the internet about this subject then you will find studies and papers on the subject of wireless charging.
All science data on this subject indicate that wireless charging is fine for phones and does not deteriorate any more than plugged in charging. However lithium battery technology has a limited amount of charge cycles guaranteed, and batteries will deteriorate over time.
Many comments state that it can be better to wireless charge, and especially if you use it to place your phone when it drops below 50%.
The optimal level of charge to slow down a battery deterioration is between 30 and 80% charge. So if you keep your phone between these values all the time, it will give the best battery and slowest rate of deterioration.
Batteries don't like to be discharged too low <30% or left continually at 100% with trickle charge. It won't overcharge your battery by leaving it on, due to the protection circuits in todays chargers and phones, but it will continually keep topping the battery level up... which is not great for long term lifespan.
So in an ideal world, you would not leave it overnight on the charger and unplug it at 80%, to then return to the charger at 30%. Whether you do this with a plugged fast charger, or a wireless charger does not make any difference.
Kind Regards
Smiley 
To be honest, I have not been a big fan of wireless chargers in past years. I always found them slow at max 7W charging, and when compared to a wired connection.
The 15W charger with my S10+ would charge the phone in approx 2 hours, but wirelessly would take more than double. This is still the case.
There would also be some mornings where I would expect my phone charged, and due to it being slightly misaligned on the pad, it didn't charge and i was left with a flat battery first thing in morning.
Now I have an S21 ultra, Buds Pro, and a watch 3. With the watch 3 I received a free gift of the Charger Trio. This is a good piece of kit, as I can place all three items on there and they all charge simultaneously. Would I pay £89 for it... No. However as a freebie it is great.
This charger is supposed 9W fast wireless charging, but this is slow compared to 25W wired. Actually weighing up the charging time of all three on their own charging cycles, of 1.5 hours for the phone on 25W plug charger, 2 hours for watch, and 2 hours for buds, then it is saving time putting them all on the pad rather than individually.
So right now I am giving wireless charging another try... and it seems to be quite good in this configuration.
Smiley
