i'm in a fair few groups - a group of my friends, a work group, an old works group, a cousins group, a family group, a 'boys chat' group, a footy chat group, a gaming group, etc...
a new message pops up on average probably every 30 seconds, and if i don't check my phone for an hour i can have 100's of messages from various groups.
i have whatsapp on silent, so i don't get a buzz/beep each time i get a message, but i just check my phone every few minutes and catch up on the various messages that have been posted, and post my replies to each thread.
Lighting the screen every few mins will be far more battery intensive than a single beep.