10ft is popular, but the biggest concern is are your beer lines going to be refrigerated? Theres a thread on 'For all you guys with 10ft hoses' (too lazy too look and at friends house on phone) that has link to a calculator. If you insulate your lines it shouldn't be that much of an issue. Be sure to post your setup ! ( show us your kegorator, again too lazy at the moment... posting on even windows mobile devices sucks).