Is it okay to low power mode frequently?

Grjtsng wrote:

I also noticed that even when I don’t use the phone especially at night the battery still runs low

Put it on the charger overnight.

When to charge your iPhone or iPad - Apple Community

Then it's time to spend $49 and have Apple or an Apple Authorized Service Provider replace the battery. Once batteries are degraded, things only get worse. They can swell, destroying the phone. Either have the battery replaced or consider a newer phone.

If you don't mind certain features to not run on your phone, sure. The real question is why do you need to use Low Power mode frequently on your iPhone?

Doesn't matter when you bought the phone. iPhone 6s was released in 2015, so it's an old phone at this point whose battery is clearly in need of being replaced.