Definitely consider a back up plan in case your computers/internet failed.
Do you back up the data daily to another storage option? If I was running from a single computer, I'd routinely back it up once or twice a day onto a portable hard drive.
Where I live, we have no landline so I use a satellite/mobile based broadband system. I use a very basic cloud based system to store records and appointments as I'm mobile (not suitable for busy salon) but I can access it from any device so that gives me more flexibility if my main device failed. (They're all Apple products so share data very easily)
Also, I can use a different mobile internet provider to access the cloud storage if I couldn't get a signal from my main internet provider.