My personal take is, don't fight Verizon on whether or not the phone has to be on an active line, just swap sims, very quick process. If I were you, what I would try to do is to push them to reset your upgrade date, arguing that you have received 8 clnr, all with problems. Then just keep explaining problem after problem with each phone and saying that the refurb process on verizon needs work, blah blah blah. I can almost guarantee you that at first, they will say no, but keep at it. repeating the same stuff over and over. After an hour or two, they may agree. or they may not, in which case hang up and try again. imo, i think that this would be a much more beneficial effort as you actually get something. you can also try to get them to send you a clnr hd maxx, which at this point, would be new. most likely, neither option would be easy to get verizon to do, but i think that it would be possible.
one other thing, if you decide to buy new and you want to get new replacements for as long as possible, buy from Costco wireless. they offer a 90 day return/exchange policy and during that time, you will get new devices. after the 90 days is up though, you are stuck on Verizon's clnr, but still beats verizon and other 3rd party which is typically 30 days or less. and the new replacement is a full retail box new replacement with all accessories.