This isn't addressed to anyone in particular, but it's a common question: does software get old and wear out. They ask because their computers have gotten slower, or features have stopped working. Their main reference point is mechanical systems, of course.
The short answer is "no", but the more complex answer is that systems change, and software can become obsolete. How do systems change?
There are "environmental" changes in CPU speed, memory price, and disk speed and price. These things cause programmers to write code that will push more data around, mostly to enable "user friendly" features, or new features requested by management (or users). If this newer software is running in an old environment, it'll feel slow because the amount of data being copied is greater.
This newer software is introduced into the older computers via updates, like Windows Update, which installs updates automatically. So while the application in question may not be updated, it's likely that the operating system has been updated, and is consuming more resources.
There are also external factors that cause perceptions of decreasing speed:
* Installing a larger monitor may be taxing the video card. This has nothing to do with the software, but it makes the software appear slower.
* The network may be congested. It's not a problem with the computer, but with the network, but it's sometimes hard to tell the difference.
* Using a faster system can also cause a perception that their old computer is slowing down.
Finally, it's also possible that the software is getting damaged.
Software installations may become damaged over time, with some software becoming disabled. This is pretty close to software "wearing out", except that the software can be re-installed and thus, repaired. While a re-install will speed up the system, the odds are, it'll never be as fast as possible, due to changes in the environment, as described above.
Sometimes, the "fix" is to install an old operating system, run the old software, use firewalls and don't read web pages or email on this computer. Then, you preserve the old environment and the old software, and it should be as fast as before. Eventually, though, the hardware will fail, and it won't be possible to run the old software on the new hardware. It may require an emulator, which may be faster, or slower, than the original computer.