I generally know about trips a month or more in advance, though final confirmation doesn't often come until the last week or so, but that's more likely to result in a bonus week of being in Ottawa rather than a surprise week of not being here.

I do not travel (for work) more than two weeks in four (as a negotiated rule with my boss after things went too crazy at one point and I got sick). It doesn't usually quite make it to that level of travel, so probably about 60% of the time here in Ottawa.