Regular cleaning will help to extend their work-life. Clean your saws after each use to rid them of dust, chippings, and filings, which can make a hole saw bind (get stuck) in the material it is cutting or even strip and damage its saw teeth. Once a hole saw has been dulled to uselessness, it is difficult to resharpen it.
Clearing chips
When using your hole saw, remember to back the saw out of the hole every so often. This will help clear the teeth from chippings and sawdust, keep the blade cool and reduce the chance of tooth damage.
Instead of backing the hole saw out, you could reverse the direction of the hole saw and clear chips this way instead.
Even pressure and balanced teeth alignment
When working, apply even pressure and make sure the hole saw teeth engage with the workpiece evenly. This will help to reduce erratic sawing action and prevent tooth strippage.
Lubrication
When cutting metals, use a high quality cutting oil to assist with clearing chips. Cutting oil ensures a smoother cutting action and creates less friction, helping to keep it cooler which will extend the working life of your hole saw.
Sharpening
There are several ways to sharpen a hole saw (all of which are quite fiddly and time-consuming). It is popular opinion that because of the relatively low cost of hole saws it is preferable to replace them when dulled.
If you do want to sharpen a dulled hole saw, then you can use a hand file to resharpen each tooth. Small diamond files are best for this but the process may still take some time and effort.
If you have access to a hand-held electric grinder, then you can also use one of these to sharpen the teeth on your hole saw. Although slightly quicker than hand filing, this will still take time and concentration.
Another option for sharpening hole saws is to use a bench grinder. If you attach the hole saw to a rotatable vice and then angle the teeth into the grinding wheel, you can put the sharpness back onto the hole saw. This is also time consuming and requires concentration.
If your hole saw has hardened teeth that have become dulled, it may be impractical or even impossible to sharpen them properly.
Replacing
Due to the amount of wear and friction a hole saw is put under when in use, it is much more likely to need replacing before the arbor does. This is an advantage when you have a detachable arbor but may seem wasteful if the arbor is fixed.
Wear and tear
Visually inspect your tools before each use for wear, tear, and damage.
Storage
Store your hole saws in a secure, dry place to reduce the risk of them being damaged or corroded by the elements.