The fresh fluid concept is unrealistic and entirely ludicrous with most transmissions, conventional or CVT. The key is to service the transmission per the OEM service intervals, with the approved fluid fill, along with a fresh filter and pan cleaning at the service.
My recollection is that Ford does not require a fluid change until 150K on the Freestyle's transmission, which is the ZF CFT30 unit, provided that you do not tow nor operate under the listed "special conditions." If you wish to practice a more frequent service interval, then a fluid and filter change every 50,000 miles would be quite conservative, IMO.
Also, the term "sealed transmission" does not exist. All transmissions are serviceable; it's just that some of them may require more effort to refill and find the refilling plugs.