@Ryan1762 As you say, it would be rare if you needed to access these areas during a guest's stay, and it doesn't seem much different than a host having to enter an entire house or apartment listing if there was a problem with the water heater or the furnace. For something like once-a-year maintenance, of course,
you'd need to block off days that would happen on your calendar so someone couldn't book for that day.
I'd just make mention of it in the listing- that if there were an emergency situation, you'd need to access those areas. And if you did need to go in there, texting or messaging the guest first would be the appropriate thing to do, unless it was a true emergency.