Ok, my argument for why 30 (resort) and 10 (offsite) is not appropriate.
Disney wants you to pay at 45. This is a no-brainer. FP window for resort guests should be longer than 45. Because, they want you to be thinking about your trip, and have exciting things planned on it, before that big bill hits and you have to chunk out $5,000. Otherwise, if FP is at 30, when 45 hits, people might think... Oh, money is tight, and we have 2 days at Epcot, so we can cut that down to 1 day, shave off here, and pay $4,400 instead. Done. But... by it being 60, now the thought is... "Oh, money is tight, and we have this day where we're doing Soarin, Nemo, and Figment, and this day where we're doing Test Track, Mission, and Spaceship... which should we cut... hmm... nothing really works. Ok we'll keep it. Pay $5,000.
So Disney did not "lock you in" per se, but they want families thinking about their trip before they have to pay their trip off. They want you to have things booked... so you are not sacrificing just another day at a random park, to instead.. be sacrificing riding the Mine Train and visiting Rapunzel. By having activities planned, you are much more likely to keep what you planned, or even try to add more.
10 days is awful. By 10 days, it's now last minute. People should have their days planned well before this, cuz by day 10 you are practically in packing mode, trying to get advance homework done, trying to meet teachers, tie up ends at work, etc. The 10 days immediately preceding a trip are not best spent planning the trip any more. That should have been done a month ago.
So. I still think 60/30. I strongly disagree that your 30/10 is better. Above are just a few reasons.