By the end of this year I will have spent over 6 weeks traveling for work, between conferences, workshops and research-related trips. Most of that travel was concentrated in the summer, but not all as I will be away for the first week of December, for instance. Minor home crises while I travel aside, that's 6 weeks that my wife has to single parent, six weeks that I can only Skype with the Wee One* rather than tuck her in and six weeks that I will sleep in a bed not my own.
Even though the amount of travel time I've had this year has put a burden on the family, 6 weeks hasn't been that bad. I arranged to not be away for more than about a week at a time and avoided weekend as much as possible, when I have the most time to spend with my family. What concerns me is that everyone I know who's lab moves at the pace I aspire to travels far more than 6 weeks a year. From my informal survey, the range seems to be between 2 and 6 months of travel per year when all of the trips are considered**. Most people don't keep up a pace at the high end of that range for very long, but many seem to have years where things are clicking and everyone wants a piece of them.
I am fortunate that, at the moment, my wife's job does not require a lot of travel but am acutely aware that my travel has a wider effect than where I sleep. I know that thousands of people do it every year across all manner of professions and they seem to make do, but in talking to several successful senior colleagues recently they have all mentioned the adverse family consequences their hectic schedules have had on their families.
As my schedule slowly fills for the summer of 2010 these conversations are one more thing in the back of my head as I wrestle with what I define as "successful" at work and at home.
*She doesn't quite get the whole Skype thing yet. Half the time she keeps looking behind the laptop to see where I am and the other half she spends hitting random keys on the computer. We're working on it.
**Hats off to those of you with a two-academic-career family, or any situation where a couple both travel heavily for their work.