DCX3400 Continued Support

I currently use a DCX3400 model cable box. It's getting old and sometimes responds slowly when using the DVR fastforward / reverse / pause feature when watching live programs. I am not interested in the newer model boxes, so I am considering buying a new (unused) DCX3400, but how much longer can I expect comcast to support this model? Does anybody at comcast know how many years xfinity will work with the DCX3400? Thank you.