i've got a carbon frame and recently purchased an aluminum frame too. there's no doubt in my mind that the aluminum one will outlast the carbon one, but then again, we live finite lives and our active cyling lives are shorter, so how long, realistically, does a frame have to last anyway?
i can find little difference between my $300 no-name Chinese carbon frame/fork that has worked out fine and my recently purchased Performance Bike Ascent $69 dollar aluminum frame, which no doubt will outlast it and suffer the indignity of becoming a resident of the nearest landfill upon my demise...
as the OP says, ride both, make a choice.