I don't disagree with you on this point.
Tivo has/had a similar issue with their definition of lifetime subscription.

In the early days of Tivo you could transfer the sub to a newer box if you ever upgraded.
That agreement is still in place for older Tivos bought AND lifetime sub'ed before Jan 2000 or similar date [and its a once only transfer, subsequent transfers don't count towards keeping the lifetime sub].

For all users since then, the sub is the lesser of:

1. The lifetime of the current box (outside warranty perod).
2. The length of time the current owner owns the box.

That means with a Tivo if I lifetime a Tivo I bought, then I **choose** to upgrade it later on to a bigger/newer box, that I cannot move the lifetime sub.
This sub stays with the original box, BUT only as long as I own it.

If I sell, give away or whatever my older box with the lifetime sub, the new owner has to pony up for a seperate sub - either lifetime or monthly.

If the box dies outside of the warranty period, forcing me to buy a new Tivo - well its like I bought/upgraded to a new Tivo.

Replay is pretty much the same.

In any case any transferrable lifetime sub will only be transferrable within the same model as you currently own, e.g. Replay 4000 -> (newer) Replay 4000, not Replay XXXX -> Replay YYYY (where XXXX is a different model from YYYY).

Basically, with these lifetime subs [and insurance in general], you pays (or not pays) your money and you takes your chances.

If you don't feel like gambling on your new box staying alive for 2 years, go monthly, if you still have the original box after 2 years, you will probably want to upgrade it to a newer model anyway (if there is one), hence the lifetime sub would be useless.
If Replay gets sued out of business within 2 years by the MPAA - then your lifetime sub is wasted, go monthly.

Really, if after 2+ years of monthly subs, you still have the same Replay TV and the Replay TV is still a valid SonicBlue product and they are still honouring their subs for lifetime owners, then you could feel ripped off maybe.
If none of this comes to pass, then you're better off (slightly) than a lifetime sub owner.