Well, I just had my call to Shaw Direct. Luckily, I had read this thread and was prepared for what I heard.
They will replace a single 630 for a refurbished 800 series PVR; but I was told it was for as long as I'm a S.D. customer, no end date. Any additional 600 series receiver that you own will not qualify for free rental. That means an additional monthly rental cost as well as the existing multi-receiver fee, I assume? - I forgot to ask about that $6.00/mo fee.
My first solution is to accept the single swap for one receiver, then start using Freerange, or Curve, or whatever the heck they call it, to watch whatever channels go bye-bye on the old 630 I keep.
My second solution, once the ground thaws, I call Bell ( ugh ) and ask if they could run that fibre at the end of my driveway up to the house. Perhaps at that time, I could first call S.D. to tell them of my plan, and maybe get a retention deal for the second free rental. That'll keep me until some cosmic mishap blows out G1.