Hey V8Dave; welcome to the Forum. As posted elsewhere, how long a battery will last when the vehicle is parked, depends upon several factors, including the ambient air temperature (hot/cold/fluctuating) and if the vehicle is stored inside, out of the elements. Yours is inside a storage unit and hopefully it'll be kept consistently warm, which will help.
You mention the possibility of leaving the trunk open. There's a manual trunk release "loop" located behind the driver seat and behind a removable side cover (check your manual), so you can open the trunk to access the battery area, even w/o power. Also and this likely won't apply to you, but beware of rodents (mice) who might enjoy nesting inside and eating car components. If you're not covering the car, I'd not want the trunk "unlocked" in case it pops or is pried open enough, to allow rodent entry. They could get in other ways and some people will stuff their tailpipes with steel wool to discourage access...or put poison on the floor around the vehicle. Some use mothballs to deter rodents, but I find their smell too offensive.
Before parking your vehicle or when you go to unpark it, always watch for the telltale sign of mouse droppings. Growing up with farm access, I saw several vehicles "ruined" due to the smell of mice who'd long since died inside a vehicle that had sat for a long time and in higher temps. Not pretty.
Personally, I'd consider disconnecting the battery, rather than let it sit "active" (slowly drained by onboard computers), to improve the chance of it starting after a month. But you decide if the risk of a dead battery, outweighs having to reset things once you go to drive it. I've left my battery disconnected for several days when I was installing sound insulation. Everything worked AOK when I reconnected. But if your storage unit is consistently warm/dry, you've got a better chance of it starting after leaving the battery connected. Good luck and hope it works out for you, whatever you decide!
