Does iPhone Battery go down when turned off?

[Samantha]

I'm going to a concert tomorrow and I was wondering if the battery will stay at 100% if I keep it off for most of the day. I'll be there for 11 hours, with obviously no way to charge...any help, or tips to keep battery up, part from brightness and wifi off would be appreciated Also, I'll me taking pictures and videoing during the show, so can any one guess how long it will last?
*be taking pictures,
And obviously, I don't have two spare phones, so USEFUL and accessible tips would be extremely helpful and muchly appreciated

 

[Ali]

Hi dear one.How ever it,s a good cellphone with a good stand by time energy saving,with so much work,I think it,s better to take two more spare phones with you!Good juck.So long.

 

[Sarah]

i dont think so but turning it off and turning it on will use a bit of battery

 

[16yearsboy]

Dont use flash, keep phone on flight mode