Leisure batteries

Swifty 123

I am quite new to caravaning and have just booked my first CC rally for this August and looking forward to it, my question is, as there will be no electrical hook up, like on our usual club sites would a 100AH leisure battery normally last the full weekend,
it is in August so hopefully the heating should not be required, so was wondering what sort of life in terms of days we would be looking at, the battery is about 2 years old so it is still in vgc. Thinking of trying some of the quieter CL sites too this year
without EHU, so I guess having a spare for then may be a good idea. Roll on summer