I'm probably getting one of these soon in PHEV and I have questions

In australia, and this thing has everything that l need. room for the kids and their stuff and its a plug in hybrid so that l can do town driving in EV and long trips will switch to petrol. From what l've read, it can do about 80km on EV mode so if i keep it charged then it shouldnt get much petrol use right? Does anyone else use these as a family mover and whats your experience been like? what happens with the 12v battery if it hasnt been driven in petrol mode for a while?

mostly wanting to get people's actual lived experience with these, thanks
ETA: it will be a 2018