How to Maintain Good Battery Life by playing PUBG daily

Hi,

I have iPhone XS MAX.

I have started playing PUBG and my battery health reduced to 99% after a month of playing PUBG.

Why ? Because I dont play any game other than PUBG and usually use the email and document and whatsapp. I was able to use iPhone for about 1.3 day for almost single complete charge cycle - (10% to 100%).

Since i started playing PUBG, i was able to use the mobile for about 0.8 day for that same charge cycle thats why i think charging again and again, with the time battery health will off course decrease.

My point is :

How i can maintain good battery health while playing PUBG ?

What i'm doing at the moment, when i start PUBG. I connect the mobile with charger and keep it power connected until i stop playing and stop the application. By doing this, when i open battery status i only see 1% battery is used by PUBG and shows ( connected to power ).

Is it saving my charge cycle ? which will increase the battery life off course.

What do you suggest ? to maintain Battery Life while playing PUBG or any other heavy game.