If you own a business or just have a WordPress blog, it is going to be important to you to find a company that boasts a very high uptime. You do not want your visitors to try to go to your website and find that it is not there because your hosting service is down. This can cause a loss of business to your website if there is too much down time where your website is not accessible.
Linux has a reputation for being reliable with very little downtime. This is because Linux only has to reboot after a kernel update. There is even a utility that can load and execute the new kernel without resetting the hardware. This allows for the possibility of a Linux Hosting server having an uptime of years.
Most hosting companies will have statistics to view about their uptime. If you want to ensure that your website is always up, look for a company with a good reputation for having a high uptime.