I usually cowash in the morning unless its hot and I want my hair down or I'm going out and want/need to restyle my hair. On a normal week if I wash (Day 1) Monday morning I'll wear it down during the day then pineapple and cover that night. (Day 2) Tuesday I take my pineapple down and usually have better hair than Monday cus the hair is stretched and has more body. That night I repeat my sleeping process and (Day 3) Wednesday I might have 3rd day hair good enough to wear down if not I put it in a high pony tail. Sometimes I might chose to wash this day if I'm feeling like my hair needs it. (Day 4) Thursday morning id usually wash again and repeat my process.
Personally I don't think its harmful to cowash daily if you're cone-free.