There is no restriction on using a monitor for 24 hours per day. However, maximum lifespan of panel is around 30,000 hours in its best case scenario. A safe rule is up to 20,000 hours.
20,000 hours equal to 2.2 years of non-stop operation, yet the stress put on all the other components which can make this period even shorter.
If you do decide to use the monitor on a 24 hours per day, please make sure the entire display is refreshed to change every 10 minutes, and no static image remains. Such as using a screensaver, power saving to put the monitor on standby, or run a completely different wallpaper or background. This is to avoid image retention. Image retention is a technological limitation of LCD monitor.