LS, chains last a lot longer if you look after them. There are two elements to this. First, use a proper chain bar oil, not engine oil. It has an additive that makes it stick to the bar, so the chain ends up actually oiled, not just spraying oil around but having its pivots almost dry. It is wear between the pivots and pins of the chain that cause it to go out of pitch, and ruin the sprockets.
Second, keep the chain sharp - which means never letting the chrome peel back from the edge. Just touch it up the moment you feel it cutting a tiny bit slower than when you'd just sharpened it. You can do this wherever you are, provided a car battery is nearby (preferably still installed in the car). Each time you sharpen the chain, you move a bit further down the slope of the chrome-plated teeth, and that means the depth of cut is reduced (depth of cut is the vertical distance between the cutting edges of the teeth, and the depth-bars (which Igor calls rakers). When this distance decreases the rate of flow of woodchips decreases, so you need to joint the chain (grind down the depth-bars) when you have ground back the teeth perhaps a fifth of their original width. That means you will joint the chain about four times before it has run completely out of teeth and you throw it away.
Whether you need to do bench work on the chain, or just field-sharpen it over and over, depends on how accurately you field-sharpen. I prefer not to joint chains in the field, though I do it in a farm shed, so I suppose there isn't much difference. I did once joint a chain in the field, because it was on someone else's saw and he didn't seem to know about either sharpening or jointing. It took nearly as long to get his chain into shape before we started, as it did to fill his horse-trailer with firewood. Probably most people would prefer to do a slow, careful job in the shed and a rather quick one in the field, and you have to clean the chain, inspect it, adjust the tension if your bar oil has let you down, etc. These things are best done in the shed. So, I always used the 12 Volt hand-sharpener whether in the field or the shed, but I did a shed-job whenever I needed to joint it, and in between if the chain had loosened at all. Remember, a loose chain is a sign of oil failure or dirt on the chain: either way you need to improve your procedure to make it a rare event. Essentially you just watch the chain teeth getting narrower, while biting your lip and thinking that eventually you'll run out of tooth and have to buy a chain. Buying consumables like chains is an irritating experience.
I have doubts about the cordless sharpener, simply because I've found the 12 Volt sharpener draws half an amp or more, and while the battery charge would probably last through a touch-up sharpen, I doubt it would last through a jointing job: that one really makes the grinding-dust fly. Igor's solution of using a file probably works, I just hate to use a file on chain, because the chain is hard and the file suffers rather quickly.
Deejay, I agree a video is needed but I can't help. I no longer even own a chainsaw: gave both of my last ones away when I sold the hobby farm about 7 years ago now. It's amazing how much stuff you give away when you ditch the farm - star-post extractors, fence wire tensioners, backpack sprays, you name it. At least I sold the tractor.
