How much downtime is acceptable for an online backup service?

I recently started evaluating options for backing up Linux servers (entire file system) to the cloud. The provider we chose claims 99.9999% data resiliency and seem to have a good reputation. However, within 24 hours of opening an account, my initial backup stopped working because they had a planned 8 hour outage. There is another 4 hour outage planned for 4 days from now. When I contacted support, they replied that "maintenance and downtime is simply a fact of life" and that "This kind of maintenance downtime is _Extremely_ rare; normally occurring a couple times per year". To their defense, they also said that "if you were in a bind we would almost always be able to work with you to get you your data even when the system was offline". Does this seem like a reasonable amount of time for backups to not be accessible?