i would put them on now as thay will throw flights if you dont, i put mine on as soon as thay are weaned, thay can still see to get to drinkers and perches as it does not have to be pitch black, thay need 8hrs of daylight, 8-4 or 9-5 i take mine off 6 weeks before first yb race, this way thay will hold flights till the last few races, i have been on the system since 1986 winning yb ave most years or ru,