The half life of ADEX is 50 hours, so after 2 days there is still half the dose available in your blood. You can do 1mg EOD day,but what i have seen the typical dose is .5mg ED or .5mg EOD depending on how much aromatasing compunds you use.You would really need a blood test for estrogen levels to see how much you need.
Excretion
Eighty-five percent of radiolabeled anastrozole was recovered in feces and urine. Hepatic metabolism accounts for approximately 85% of anastrozole elimination. Renal elimination accounts for approximately 10% of total clearance. The mean elimination half-life of anastrozole is 50 hours.
http://www.rxlist.com/arimidex-drug.htm