@Eawo Domoticz groups sensors after the order you present them in, see: https://forum.mysensors.org/topic/5132/ds18b20-ans-sht31-d-show-up-as-combined-sensors-on-domoticz/15
I send every 5 minutes and check the value before so that I only send if the value has changed
I have been running my sensor for nearly 2 months now and battery level has only decreased 1-2%
Make sure you use 1 MHz bootloader