i used to sharpen alot back when my EDC was an opinel. the edge retention on that wasn't awesome-decent, and adequate-but not awesome. i carried a small soft arkansas stone in my pack pocket or pack and touched it up as often as twice a day or as little as once a week.
now that i carry a stockman that has better edge retention i sharpen probably once a month or so (that is-my own knives. i sharpen lots of other knives). i use the main blade about 98% of the time, and don't obsess about keeping it hair popping sharp all the time. every once in a while i strop it to keep it in good shape. i know that the blade will cut well even when its a "little dull" (which is still 100% sharper than alot of people's kitchen knives) and i know that if it isn't sharp enough to do the job i have two other blades handy.
as for my fixed blades-i have been carrying a scandi for a while, and i really don't like sharpening scandis. this means that i put off sharpening for as long as i can, but even when i decided that its time to sharpen it can still usually slice paper cleanly. i often strop in between sharpenings to keep the edge in good shape.
i used to really obsess over keeping my knives crazy sharp all the time, but i realized that its a bit silly to sharpen after nearly every use. with my stockman i can always keep a stupid sharp edge in reserve, which solves a dilema for me (what if i need to perform emergency surgery?!?!). i like to step back and take a look from a different perspective...even when i call it dull 90% of the population would still call it stupid sharp.