We always carry a spare bottle. We've just finished a 6Kg bottle having used it for 5 full weeks and several weekends away. Have only really had to use gas for cooking on the full weeks as had EHU but not EHU for weekends as mostly C&CC rallies.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.