More than 1 bath a week is only in a extreme necessity or emergency...the skin needs time to replenish the oils before you wash it again. Also human shampoo is extra harsh on yorkies skin, the ph is also different...so if using human shampoo dilute it a lotttttt of choose a neutral ph shampoo.
I bathe Mojo as needed, which is at least 7 days and the max of 15 days
So it is really depending on your necessity...the only think i would be careful is with excessive bathing...