The tire only need a few psi to keep its shape with no rider on it. So I would be surprised if the tires actually ever got that flat.
And even if they do go completely flat, tubes and tires can both be folded up for long periods of time with no ill effects.
The only situation I would try to avoid going completely flat would be a sealant-based tubeless setup. It would most likely be fine, but there is an off chance you might break the bead seal when you go move the bike around. But again, not a catastrophe if it happens.