Most computer mice are quite reliable. Today's models that use lasers instead of rolling balls should last for years.
A wireless mouse will need new batteries every month or so, depending on how often the mouse is used. Some mice will warn you when your batteries are running low. Some won't.
However, even the best of mice will stop working unexpectedly, either because of a malfunction in the PC or mouse, or even because of some wacky stuff built into the page you are trying to copy from. Sometimes mice can be brought back to life by thumping them on the mouse pad, briefly removing batteries, or re-booting the PC.
If you're in the middle of some important copying-and-pasting, and don't want to take the time to re-boot or hunt for batteries or do other techie stuff, you can always revert to keyboard based functions.
Here are the basic Windows commands:
CTRL+A; select All
I actually had to use shortcuts to paste the list into this page. There may be similar shortcuts for the Mac, but I don't speak Applish.
Photo from SuperStock.com. Thanks