Acceptable level of ping time outs to internet?

We have a new cloud-based record system that has had many problems with users getting disconnected. The vendor says this is because any time there is an interruption in internet connectivity, the connection to the cloud-based system drops and the user gets kicked out and has to reconnect  to it.  i did some continuous ping tests to their cloud server and saw an occasional reply time out, maybe once or twice in 15 minutes.  They said this is enough to knock the user off, which is what's causing all our problems. We've not had this problem with any other internet-based activity.  I've done similar ping tests to these servers from some of our other locations, as well as to google.com for comparison. All of them occasionally get a reply timeout.
So how realistic is it to expect that the internet connection will essentially never time out? That's the standard that the vendor says we have to meet, but that doesn't sound realistic to me. Since it is timing out occasionally, what can we do to stop it?