As long as you can get replacement parts, a power tool can basically last forever. On corded power tools, the carbon brushes and bearings would be the first to wear out followed by the other less obvious items like the trigger switch and chuck.

While bearings are pretty standard industrial size and can even be an upgrade to the original bearings that came with the tool - as manufacturing tolerances and material improves, you might start to run into problems with older tools for other wear items.

Unless you can find a donor tool or a cache of genuine spares for a particular power tool like this guy did, then it's pretty much game over for your tool.