Time will tell how robust these are and if there are any failures in continuous use... Initial results from the field are good however.
We connect these in a depth-2 tree. One 1:8 mux is the top-level switch, with the remaining 5 providing 40 input-channels. This easily expands to 64 channels by adding one more 1U box. Beyond that I guess a depth-3 tree connection is required.