Haven't they already said month to month is going to be more or are we talking going in and buying one back issue? I thought the whole DDI thing was pretty much like Steve Jackson Games pyramid where you got access to the 'vault' so to speak.
I mean people who do not subscribe but buy the compiled PDF issue. If they call them back issues still because you cannot buy them during the release month, or current issue because non-subscribers can buy the compiled issue during release month is yet to be known. Likewise if they are still going to allow non-subscribers to buy single compiled issues.
I would hope that a compiled issue for a non-subscriber would cost less since the overhead of leftover issues does not exist as all issues will always need to reside on the servers for subscribers, and those who did not subscribe for that month, but prefer to buy the finished issue do not get the bonus tools or compendium.
So not buying a month of time from DDI, but buying the single compiled issue when it is released. Say a single issue of Dragon, but not Dungeon.
I wouldn't count on the compilation products to have 100% of the content. I'd expect more of a best of type thing.
As for length, I seem to be getting more than $5 per month of value from the combined magazine(s) and that is all that really matters to me. Would I like some changes and more value, sure? But, am I getting at least $5 worth of value, sure!