Now you have a kid. That 108 hours just turned into 80 or less - much less in the early stages for just about any parent, still less for at least the next decade even if you're a selfish parent. What's left is no longer movable from earlier until later, or from one day or to the next, because your child's schedule is not as flexible as an adult's. You practically never get to sleep in past 8am. When you do it's because you owe your spouse a favor - and with everything else in the paragraph it's a big one. It's impossible to do anything requiring intense concentration, because your child is a high-priority interrupt and that interrupt triggers frequently. My daughter (seven) is far better than most at staying occupied by herself, and even she interrupts me all the time. You know that look you give your coworkers while they interrupt you just when you finally got into the coding groove? You can't do that to your kid, so you don't even start anything that intense. You code less, you read less, you exercise less, you game less, you get online less. Your only real opportunity to have a significant block of free time is after the kid's in bed. To take advantage of that you'll be dipping into that 56 hours per week of sleep time and using caffeine the next day to (sort of) make up for it. By the way, I hear all of these factors are compounded when you have more than one kid, and I just can't even imagine what it's like for single parents.
I'm not complaining. There are other things that more than make up for the loss of time and control over time, but it's still draining. Still, I just have to laugh at the childless people who just assume all that time is available and flexible, who don't realize that being able to ride their bikes three hours a day or spontaneously head out for a three-day binge in Vegas is a luxury. Enjoy it while you can. Enjoy it your whole life if that's your choice. Just understand that every parent in the world is going to have a different perspective on free time than you do. Even though the result is worth it, losing two thirds of your usable free time is hard.
When our kid was still sucking his mother's milk we went on 5 days trip in Dali, Yunnan, rented a 4*4, went to cheap backpackers hotels, no problem at all. The only diff was to wake up earlier than we would without him.
For the interruptions, why do you allow them? When my dad was working at home, we wouldn't enter his place without a reason.
I think a big issue is about a new kind of culpabilization of the parents. Mothers need to be perfect mothers. Fathers need to be perfect fathers. Kids are supposed to be perfect kids. That's ok, but can be dangerous if taken to the letter and too seriously.
If your child is a different age, or has siblings, or is even more exceptional in terms of self-entertainment, or if you're content to plop your kids in front of a TV/computer for hours on end, or if you have other family/friends willing to take your kids often, then maybe you're able to achieve longer periods of concentration. Good for you. Please don't assume, though, that your circumstances and thus your choices are applicable to others. Among the hundreds of other parents I've talked to, this issue of limited and fragmented free time is a major challenge for every single one.
As for interruptions: I know grudgingly admit that I have to go to CoWorking spaces or an office to work. (Granted, that is also lost time for the commute).
Maybe exercise could be build into the kid time somehow?
Also it might make sense to take turns with the spouse to create more free evenings.
Where I live, most kids also seem to go to kindergarden from age one, which seems rather early to me.
My wife and I have an 8-month old, and she's a reasonably 'easy baby'. But even so, from a coding perspective, the non-maskable interrupt thing is an absolute brain killer. And it's more difficult to get in the groove because of the sleep deprivation.
From what I see above, there's a lot of encouragement here that the instant love/bonding thing will make the whole experience worthwhile. That may be true. But there's also a lot of self-censorship (or even explicit censorship : search for the word 'disgusting') about how draining the whole thing can be. And that having a baby is not a choice that suits everyone : Think long and hard about whether you really want to give up two thirds of your usable free time...