Your file looks quite rusty in the pictures. Files are usually made from high-carbon steel which is quite prone to rusting if stored in a humid environment. Rust will degrade the file's performance because it tends to round the sharp edges that do the actual filing.

An old trick it to rub a candle on the file before using it. It will make the filing easier and prevent the file's grooves from clogging. It might even prevent rusting somewhat.

A ceramic file won't rust and performs well even on hardened steel. A diamond-grit coated file also works well on hard materials.

You also need a flat file for the rakers on the chain. After several sharpenings, the raker will be higher than the cutter. Stihl makes a good kit that includes a file guide for the rakers.

The great thing about Stihl chains is the angle mark on the cutters. Helps maintain the correct sharpening angle.

Roland-You are right, the file I'm using is somewhat rusted and ready to be replaced. Never heard of the candle wax trick or a file made from ceramic. Now I'm wondering if it would be cheaper to pay more for a ceramic version compared to multiple replacements of a regular file?

Bob-I almost forgot about those angle marks. Thanks for the inspiration for todays post...and yes, I should say something about the rakers...maybe I can work that into the next post.

The reason why your files wear out so quickly is probably that both the file and the cutting bits on the chainsaw are hardened steel, and the file is not much harder than the chain.

I've got a silicon carbide snife sharpener that I've been using for at least two decades with no visible signs of wear on the carbide bits.

Ceramic files should last much longer as it is a lot harder than steel. But as opposed to hardened steel which typically has a hard surface and a less hard but more flexible core, ceramics are hard through and through. That also makes them more brittle. Ceramics will not deform plastically when overloaded like steel can do, they will just break. So if you put a ceramic file in a vise, and give it a good whack with a hamer, you might be able to break it. So don't try to use a ceramic file like this as a pry-bar. But if you look at youtube videos of machining steel with mills with ceramic inserts, it is not uncommon to see literally red-hot swarf (chips) coming off, so it cuts steel really well.