I completely agree with Buckaroo that it is all about finding the right balabce, and that is different for everyone. I went back to workafter my first baby when he was 11 months and worked 5 days/week 8.5 hours/day. I felt guilty because I hardly ever saw him, by the time I picked him up after work and got ome, had supper he had to go to bed. He went from 2 naps to 1 nap at that time so he was exhausted when we got home and was fast asleep in bed by 6:30 pm. I saw him for about 2.5 hours/day total and that was the time I was getting us ready for work/driving to work and dayhome/making supper, etc. Not quality time together. by 18 months he was able to stay up to 7 or 7:30 so that was better. Weeknds were spent doing all the other things you have to do. Buy groceries, laundry, clean house, any errands, and supposedly try to have time with your toddler. I got pregnant 3 months in so ended up working for 1 year before my next mat leave. Then I went back to work again when my next baby was 10 months old. I lasted about 4 months full time again, then reduced my hours to 4 days/week, but it was still crazy, so then I quite 3 months later and now work 2 evenings/week only. Reducing my hours did give me 1 more day, but at work it is worse because you end up doing almost the same amount of work. I was tired of feeling like I was doing a bad job at work, and a bad job at home. Honestly it was a nightmare, and now I don't know how I lasted as long as I did. I guess I just put 1 foot in front of the other and trudged though each day. At this time I was also getting up to nurse my one year old 1-2 times/night. The second time back at work was a lot harder than the first.
Childcare makes a big difference, I was not 100% happy with my childcare, it was "okay" but not the greatest that it could have been and I really didn't feel that putting him into a differnt home or daycare would be any better. Top notch care here is very expensive and 1 year plus waiting list to get into, and have to pay full time even if need part time.
2 evenings/ week is perfect, as don't need any childcare and lets me off the hook for the bedtime routine twice/week, and my job is fun (I teach prenatal classes so everyone is happy, and pretty low stress type of job), I have lots of time for my family and can put the children into activities and take my child to preschool.
I should add that it also depends on how much support you have. We have myself and my husband, that's it, no family anywhere near by and no housecleaner/helper/nanny.
Good luck finding the right balance for your family.