I would take about 2 weeks total. I take about 3 days for each step. I feed Jake 1 cup twice a day..so my transition goes like this....3/4 old..1/4 new for 3 days..then 1/2 old..1/2 new for 3 days...then 3/4 new..1/4 old for 3 days.. If at any time he gets an upset tummy..I go back a step for a few days..then move on again. You can add pumpkin while you are transitioning...just to help his ! I don't know about tear stains but I noticed subtle changes with Jake's new food in about 2 weeks..his was better and recently I noticed a big improvement in his coat. I'd allow 6 weeks to see full affect.