I figure all targets are disposable, including steel targets, but for the money, they last a lot longer and with lower power ammo such as pistol ammo, a target made for rifles (500 Brinnell) will last years and years and years. For rifles, such targets will last for 10s of thousands of impacts.
One alternate option I have found is a nifty moving and reactionary target made out of steel, two pieces intersecting to form an X when viewed from above and making a 3-D target. Evans Targets manufactures this design (
http://www.evanstarget.com/pages/1/index.htm , but not currently pictured on their site). The target is called the Shaffer Shifter and should be posted on their web site in February.
I have two sizes of the targets. One has an 8" diameter (target faces) 1/2" thickness made from 500 Brinnell steel for rifle ammo and 6" diameter 1/4" thick 500 Brinnell target made for pistol calibers. These are suspended from a chain from about 15-20 feet high.
The target is set into motion by manually swinging it to get it started, or can be set into motion via bullet impacts. Once in motion, the target moves most in XY dimensions, but also in Z, changing elevation during the course of the swing arc. Impacts can speed up the motion, slow it, and/or cause changes in direction. Via the motion, the shooter is challenged in sighting on a moving target that continually is changing location in all 3 directions, trigger control, and leading a moving target (from distance, although short range shots require little or no lead). This is a fun and challenging target to shoot.
In the image, the 8" diameter rifle target can be seen in the low center, hanging from a yellow chain. The last 18" or so of chain is protected by steel tubing to help mitigate the impact of high shots that might otherwise cut through the chain.
What I really like about these targets is that it is very easy to increase the difficulty level. While moving targets of these smaller sizes are challenging simply because of their size and motion, increasing distance by just a few yards increases the level of difficulty quite a bit. As distance increases, sighting, tracking, trigger control, and leading all become more difficult to coordinate at the same time.