I do that on every trip, but only as a backup, and only with section maps. Frequently here in Japan there are very nice map billboards at the trail head, showing info not found on my large scale paper maps. The scale of these billboards is much smaller than that of a paper map. So I take one or two pictures, and usually refer to it during my hike.
Here's one example; of course greatly reduced. The originals are about 3000x2300 and show up fine in daylite on my Casio EX-Z750. Second picture is how detail from the same .jpg would look on the camera screen after zooming in on a section of that .jpg.
When my camera powers off and on again in play mode, it returns to the last viewed picture, and does not extend the lens.