As long as they are well exercised beforehand and have plenty of puppy-safe boredom activities to do, is there a good reason I should go back to blocking them off? Of course I still would never leave them for more than an hour or two like that.
For an hour or two, you're probably fine, for now. However, they ARE still very young, AND, what one may not do . . .watch out for TWO! LOL Two males of the same litter can, and often do, start fighting. Too much togetherness is not necessarily a good thing. With multiple dogs, you want to ensure that they're separated for periods of time, because you don't want them becoming (too) dependent on each other, for many reasons, but also, because you don't want their bond with each other to be stronger than their bond with you. When that happens, training becomes difficult (they don't listen to you - the focus is on the other dog). Adolescense can be very trying - much more difficult than puppyhood, with lots of acting out, if you will, and "selective hearing," not to mention "forgetting" what they've already learned. Also, in case you leave collars on them while they're in the house, be sure to remove those collars when they're together. I've heard horror stories about strangulation with one dog's teeth stuck on the collar, and can't get free . . . a safety issue, to be sure.
I have 4 well-behaved dogs who all get along beautifully. Would I ever leave them all out free? NO WAY! Maddy and Beau, yes. They're nearly 8 yrs. old, and have been together over 6 yrs., and, a male and female are less likely to get into a fight. They can get pissy with each other when I haven't taken the time to give them each one-on-one time with me, so, when that's the case (I've been remiss), I will crate Beau, and lock his gate. Just in case. I'd much rather error on the side of safety. Luc (Shih Tzu) I crate because of the huge size difference between him and the Standard Poodles, and he's pretty cocky sometimes, so . . . Lucia, the puppy, though potty trained, is still a puppy, and full of energy . . .don't want her bugging the older dogs (who enjoy her very much, and I want to keep it that way), so she is crated. Safety first is my motto.
Many people can't wait to stop using the crate, and let their dog(s) have freedom of the house at an early age. I prefer to keep the crates up and in use for the duration of their lives, because, should they have to be crated for some reason, then they won't be stressed by being placed in a crate, AND, there are times when one, or more, need to be contained for a multitude of reasons.