I don't wear CROS or BiCROS aids (this will change sooner or later), but I have worn hearing aids for 15 years. If you live in a humid environment or are very active (sweating), then you do need a drying box for your aids. I have worn Widex hearing before and I liked them very much, but they are sensitive to moisture and would shutdown if I didn't dry them every so often. But after drying, they would work fine.
You only need to use the drying box at night when you're sleeping. Each night before going to bed just take the batteries out of the aids and put the aids in the drying box, letting them sit in the box overnight. That will remove the moisture from the previous day and extend the life of the aids.
Some of the other brands of CROS/BiCROS aids may handle moisture better than the Widex, but regardless of the brand you should use the drying kit to keep the aids in top working order. With the cost of these aids and normal hearing aids, a drying kit is a cheap investment to keep them working well for as long as possible.
Charles