Hondo

I think it depends on the state of the temple ^ ^
If it's an open-style tourist temple where you can go in and out freely, it might be okay to stay for a long time, and if it's a small temple like mine, what happened? It's going to be a story called.
If you know someone you know, isn't there no problem if you say hello before going up to the main hall, tell them that you want them to stay in the main hall, and then do that? The possibility of being turned down isn't zero, but rather than worrying about it, you should ask.

Nowadays, for crime prevention reasons, it's not necessarily a good thing to go in without permission during the daytime, even at night
Even at our mountain, iron doors are closed and locked at night, otherwise there is a risk of theft, etc., and if such a situation occurs, it will be involved in management responsibilities on the temple side

The main hall gets particularly cold at this time of year, it gets horribly cold, and for me in the cold, I don't know how many layers to wear when it comes to sleeping in it

Whether or not you can get permission depends on the temple, but be sure to ask for permission

Even if you get permission by any chance, please take proper measures against the cold, such as a warmer

this sentence is about to be written, isn't it?
At this rate, the meaning is a bit unclear. Everyone answered their theory of principles, but...
But it's a sentence that makes me a little worried.

　This is New Year's, so I'll write points to keep in mind when you feel like that from now on.
Basically, temples are the same public facilities as community centers and government offices, so you can enter and leave freely when the lock is open. But the manager is the chief priest, so if you want to stay, stay at the temple that runs the shukubo. There are also temples where you can stay for 500 yen. I'm staying without meals, though.
Making unreasonable demands on a monk's kindness for good is an exploitation of kindness. For now, if you have any questions about manners, please chime in and invite the chief priest who is the manager of the temple. You would never treat them as disrespectful.
I'll tell you a realistic story. If you find that you are inside the temple in silence, you are still obligated to report it. Since I'm a woman, things are extra important. Legally, not only is it an illegal invasion, but if the chief priest of that temple is a man, it is suspected that they may have imprisoned you. A reasonable amount of delivery is also necessary for the laid-back temple. There are also religious corporations that misuse it against people in need, so you should be careful about that too. Otherwise, there is a risk of double damage.