How long can it be without my tooth fillin?

Depends: If in pain see your dentist immediately. If not you can wait a day or so, but since the tooth is weakened, you run the risk of cracking the tooth, additional decay or nerve exposure. These could result in further work needing to be done besides replacing the filling.

Today if possible: Question is vague to me. But if you need a tooth to be filled in since you have a cavity and potential source of infection , the sooner you take care of it the better chance for you to salvage that tooth. Tooth are precious take extra good care of them.

See a dentist: Get the tooth filled asap. Remember a small cavity can turn into a larger and deeper hole. This will require a root canal and a crown to save the tooth. So a very affordable filling can turn into a $2500-$4000 procedure.

Not too long: A missing filling can lead to a root canal or even an extraction. It is best to get it replaced immediately.

Don't hesitate: The longer you wait to have a tooth filled, the decay can spread further into the tooth and possibly get into the nerve (pulp.) the sooner you get treatment, you have less of a risk of a broken tooth, a root canal or even an extraction. Is ti worth it?