i leave mine in the car too with windows up and doors locked

If its hot i generally will leave the windows cracked and park undercover (which najority servos have anyway) but im also lucky i fill up locally and we are only a small town so not OVERLY worried about someone stealing them or the car but i always lock the doors 'just in case' as you can never be 100% positive

with DS1 i would always do the same thing as we lived in a bigger town for his first 5 months