A lot depends on how much patience you have, how often you like to drink, and what the water sources are like. I hike a lot in the Northwest, where there are a lot of streams and lakes. I rarely carry water. So, for a typical backpack trip, I'll cross a creek, stop, get out my inline filter, drink a bit, then hike to the next stream (or the one after that). I can usually do that just fine for the backpacking part of my trip. When I make camp, it is nice to have a clean platypus. I attach some hoses, use the filter as a gravity filter this time and collect a full platypus. When I decide to hike to a peak, I just fill up the clean platypus, and enjoy the already filtered water.
Late in the year, or in areas where there isn't as much water, a treatment style approach makes sense. You are going to have to carry lots of water anyway, so you might as well treat it when you get it (since you can't get it very often) and let it activate while hiking.