One good reason to book early is for a popular route with few options.. My example is a day time flt ex-Hawaii>SEA>BOI. AS usually has only one flt per day that gets us home the same day we leave. This flt. usually departs HI ~11am>12:30pm. I grabbed 2 seats this morning using cash & a CF cert. for next Feb.6th. Yes, there may be a schedule change or two but hopefully nothing too drastic. The price of this flt ($469 for both) will never be lower, IME. The only other airline offering this schedule is WN and I won't fly them unless I'm desperate.