Okay your dentist just told you that your tooth is cracked.
He/She just told you that you need a crown.
Your first question is, "How long can I wait to get this crown"?
Well, here is the answer.
It totally depends.
Cracks are produced, and continue to move, due to pressure
exerted on the teeth. Remove the pressure and the crack stops.
Sounds easy, right?
Pressure on teeth can come from chewing, grinding, clenching,
biting tags off clothes, etc etc.
Therefore, if you stop chewing (all liquid diet), grinding, clenching,
and never again use your teeth to bite fishing line in half
then, and only then, that crack will stop moving.
Bottom line is this, get your teeth fixed as soon as possible.
Financing the work is always a factor and maybe it can't get done right away.
Just know that the dentist has no way of predicting when and where you tooth will break.
If your dentist tells you you have a crack just be very careful.