It can depend on the natural gas companies policies but most times you can go a month or two without paying the gas bill before you face disconnection of the natural gas.
During the winter months though there usually is a cold weather rule in place depending on your location that forbids the natural gas company from shutting your natural gas service off from November 1st to March 31st so you could technically go that whole time without paying your natural gas bill but then you'd have to pay late fees and then re connection fees to get it back on plush a huge bill.
If you're having trouble paying your natural gas bill call the gas company and speak with them and get on a payment plan or look for assistance through programs such as Liheap.