1) Less and more than you think. Bank on at least one to two hours out of every four (that's about their sleep-wake cycle for the first couple months). Very little of it is hard if they're not sick, but the cycle is relentless.
2) Babies are very portable for the first 6 months or so b/c they're so oblivious to the world. Wake-up, change them, feed them, interact for a while, put them back to sleep for another 2 hours and they don't care what else you're doing. One parent having a full time job is easy, two is expensive and hard. Downtime is plentiful because of the frequent naps. Ditto for exercise as long as you're going one at a time while the other tends baby and unwinds.
Ironically, scheduling is much harder once the baby sleeps through the night, because at that age they're much more alert and aware during the day and therefore need a more rigid nap time routine. It gets a little better around 12-18 months when they go from two naps to one, and even better around 3-4 yrs when they drop the daytime nap and stay up all day.
Huh. My answer (as a father of 3) to how much time they'll consume would, only slightly facetiously, be "all of it."
Your math about sleep cycles is way wrong, and the idea that you'll still have half the free time you used to is laughable. Assuming a more or less 'normal' work schedule, most of the time they're sleeping, this guy will either be at work or will be sleeping himself.
My advice is to assume that for a few years you're going to have very little downtime unless you don't sleep much or don't feel the need to see your wife much.
I'm a middle child, and yes I suffer from middle-child syndrome big-time, still. Working class background, mum was a housewife and dad worked in a textile mill. Its amazing how he managed to raise us on that salary, yet 7 out of 10 of us have at least a degree, going all the way up to at least one PhD.
To clarify, I was talking about age 0-3 months specifically. At that age, my kids slept for about 2-3 hours per 4. For the 1-2 they were awake they required attention for most of the time. So 30-50% of your clock time is taken up by the baby. So you don't have half the free time, you have half the total time.
1) Less and more than you think. Bank on at least one to two hours out of every four (that's about their sleep-wake cycle for the first couple months). Very little of it is hard if they're not sick, but the cycle is relentless.
2) Babies are very portable for the first 6 months or so b/c they're so oblivious to the world. Wake-up, change them, feed them, interact for a while, put them back to sleep for another 2 hours and they don't care what else you're doing. One parent having a full time job is easy, two is expensive and hard. Downtime is plentiful because of the frequent naps. Ditto for exercise as long as you're going one at a time while the other tends baby and unwinds.
Ironically, scheduling is much harder once the baby sleeps through the night, because at that age they're much more alert and aware during the day and therefore need a more rigid nap time routine. It gets a little better around 12-18 months when they go from two naps to one, and even better around 3-4 yrs when they drop the daytime nap and stay up all day.