I used to have an old Windows 2000 laptop without onboard WiFi that I called "Deadline" and used for the same purpose. If you have work you can do without connectivity for extended stretches I recommend it.
As long as it works, why not use the hardware if you have it and it's still operational? Older desktop PC's have a certain power usage issue compared to modern ones, but laptops usually tend to keep power consumption down.
Everyone's use case is different, but in many cases, older hardware simply isn't a limitation.