I have on occasion seen people use date filters in their segmentation smart lists. This doesn't function the way people think. Relative operators like "In Past" or "In Future" don't get recalculated constantly so people may not switch segments when you want them to.
When a segmentation is created using a date filter, it evaluates the people at that moment and segments them based on the current value. The segment the person is in only gets reevaluated when there is a data value change, which does not get registered unless the actual data in the field changes. Relative operations don't register this in the activity log since the actual field value isn't changing.
For example, imagine you built a segment with the filter "Created At in Past 30 Days". Every new lead would be put into this segment when they were first created, but they would not be moved out of it on Day 31.
Since you should really only be using segmentations when you want to create dynamic content, your best option in this case would probably be to add people to and remove people from static lists with a smart campaign and use the static lists in the segment definition instead, just as suggested when doing this with custom objects.
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