What is the best temp to hold your AC? ok i'm new to having AC within my house...i'm in Missouri and...

ok i'm new to having AC within my house...i'm in Missouri and we're averaging between 85/90 during the day... I own my AC set at 78... I was wondering what the energy investor level is? I leave my AC on adjectives day and night... should I turn it past its sell-by date at night? or is it ok to keep it running?
On average, how much do you spend on...
Answers:    i dont know what type you hold, but some really fancy new ones usually come with a standard room temp. what this does is, reguklate the temp to stay at that temp lone. so if you were to put it on say 78, but you dont want to surplus energy when the room is at that temp, then it will automatically stop heat until it recognises its getting colder! Fancy huh!