What is the average amount of time you should wear a pair of sneakers?

when i get a pair of sneakers i wear them everyday until their worn out. right now i have air jordan retro 9 sneakers and ive worn them everyday since christmas up until now. there is wear on the bottom where the rubber sole shows. should i get new ones or stick with these until they completely fall apart. if i should get new ones, can somebody hook me up with a website that offers cheap air jordans or nikes. thanks.