Subsequent books will be shorter in playtime. Producing 6+ hours on a regular basis isn't sustainable, both from a development and testing point of view. We didn't get nearly enough testing done with Book Two. We got lucky in that there are relatively few serious bugs, but there are also a number of cosmetic issues that we would have preferred — but didn't have time — to fix. We also can't keep pushing the team as hard as we've done the last two months. People will burn out.
In addition, the story changes with Book Three, getting more focused and dramatic. In terms of pacing, it will benefit us to have shorter episodes. Players were allowed to meander in the first two episodes; this won't be as easy in subsequent instalments. Things are heating up!
While I would've probably still supported RTG to the best of my financial abilities, even if I knew I wouldn't get the early access without steam, I still remember thinking: "Hey, that's so cool, it would be really nice to get things up in advance before everyone start playing, and tempting spoilers/puzzle solutions start to show up", or something of that sort. I even "sold" to others that it's a good idea to pledge higher tiers for that reason.
To be truthful, given the quality of game so far, and exceeding any expectation regarding play time, I hardly feel "cheated out" of a reward, Especially if allowing the early access would've taken time from RTG that would otherwise be invested in the game.
So you won't find me complaining about not getting early access, but be careful promising a surprise to early access backers, without specifically explaining in advance that you have to be steamers to get it as early access.
I still really hope to get that surprise early, regardless what it is, like I said, because it would be cool