If you have concerns over battery life, you might want to consider an app that supports "push notifications".

I haven't come across a free one (but I also haven't needed one in a couple of years, so one may exist), but Zoiper and Groundwire were two I've used before but this feature (push notifications) was locked behind in-app "Pro" upgrades, but they did work at minimising the impact on battery life!

Try MizuDroid. It is free and push notification too !
Battery doesnt suffer.