Tweaking an OWB for increased burn time

Has anyone ever modified the controls on an OWB to allow two stages of burn? What I have in mind is the normal burn (air open and blower on) and one with air open and blower off. Would two aquastats one for air and one for blower with the air set at a slightly higher temp. be a reasonable solution? Any method to allow burn time w/o blower has to be a plus. What is a typical stack temp. on an OWB with blower operating? The only time I ever hook up the blower on mine is to burn off creosote an that doesn't take very long. Ithought maybe some of the experts here might have some other options.