How long the wigs last are normally down to the type of hair you buy, if you are looking to buy a light coloured wig i.e. blonde then you may find that it doesn't last as long as originally the hair colour may have been very dark.
I would suggest reading the 'newbie's' threads that are normally 'stickies' in the lace front sections and also reading some posts. There are a couple of Caucasian girls on the board who have made posts but I can't remember their names.
Grab a seat and read for a day or two - then send me a PM if you have any questions