YABU
DH and I both did this for about 18 months. We moved house (to zone 3) rather than continue it any longer, otherwise it would have killed one of us.
Firstly there is the stress of getting to the station on time for a particular train (rather than just turning up at a tube station or a zone 3 train station and getting the next train coming). Then you may not get a seat, so you have a long time to stand around. Even if you do sit down, your dreams of working in that 50 mins will more likely be some email catching up (not to be sniffed at, admittedly), half hearted look through the Metro, and trying not to have too much bodily contact with a stranger who really needs a good wash.
Then there are too many opportunities for things to go wrong with your three part journey - if there is an accident on the road to the station, a delay on the train or a tube line out of action (or all three on the same day, as happened to us once...) the knock-on effect is immense. How frequent are the trains? Unless they come every 15 mins it's catastrophic to miss the one you are aiming for.
The cost of the season ticket will be immense (our parking ticket was something like £4000 a year, then a train plus zone 1 ticket was £6000 each...). If you work from home on a regular basis in order to reduce the long commute, you will be spending money on something you won't be using (that always rankled me, I know not everyone will be bothered)
Your DH will have to be solely responsible for the DC. Fine most of the time, but what's your back up plan for when he is sick, or has to work somewhere else for the day? And what's your back up, back up plan for when your train is delayed on the day you have to get back for the DC? (This is easier if you have friends or family locally - we moved somewhere we didn't know anyone, so had no immediate support network for this sort of occasion)
In short, we hated it. It felt like the worst of both worlds to us - we couldn't enjoy living in the countryside because we were always on a train; we couldn't enjoy London because we had to keep an eye on the last train home, and we still had to pay the eye-watering cost of a TfL ticket.
sorry to sound so negative!