Frequent use of Personal Hotspot.

Hello!

I had been using Personal Hotspot on my previous iPhone 6 for 2 months for my laptop, mainly to watch movies in 1080p and play some online games. I had been doing that around 4 hours a day in average, every single day during those 2 months. Also, I would like to

mention that it had been more than 2 and a half year since I bought that phone.

While I was using it as a Hotspot for my

Laptop it was always plugged in, always charging.

During that time I have noticed that condition of my iPhone battery is getting worse, I had to charge it more often (twice a day instead of once a day), often battery percentage fell from 80% to 30% in a seconds.

Battery maximum capacity is still 90% on that phone.

Recently I've bought iPhone SE(latest one).

My question is, does constantly using Personal Hotspot affect your battery life, it's "ageing"? I don't want to ruin this iPhone battery as well, since it is new.

I've read somewhere in the internet that Hotspot is designed for using, but is it designed for using every single day?

Thank you very much!

Have a good day/night!