That's not the case when on the saw for long hours though, because it takes about the same time to swap out a blunt chain for a fresh than it does to plonk down on a bank or log and quickly sharpen the blunt one. It only takes a couple of minutes to hand file an average chain.
Thinning in the forests where you're covering a lot of ground, once a new chain has had a bit of use, I start to sharpen it pretty much every tank. That's about once every 35-40 minutes with a 60cc-70cc saw depending on tree size, the bigger 20"-24" trees you'll drop about 30 an hour, average thinning size is about from 12" - 18" where 50 an hour is normal, or early thinning of young small trees that are about 20 feet tall and easy meat and 100 an hour is childs play
A clued-up operator immediately stops and sharpens the chain the instant it starts to feel a bit dull, instead of carrying on blunt, and the instant you hit the dirt is the instant you should sharpen, secret is to spend all day with a 100% sharp chain 100% of the time, not only are you using a hell of a lot less effort and a lot less fuel, but in the long run the whole saw/engine/clutch/bearings/chain/ bar etc.. all live a lot longer. You'll find chain swapping over long periods of time just isn't practical for lots of reasons, and a 'chain swapper' is always going to find himself running a blunt chain sooner or later - usually sooner!