As you may already know that graph patterns are generated whilst OpenVPN users are connected.
With that being said, do you perhaps know what could cause the graph patterns to flat-line over long periods of time whilst users are connected to the OpenVPN service and working remotely on their work computers? Also is there any IPFire guide which explains graph patterns in detail?
These graphs are generated by collectd using RRDtool.
Documentation of RRDtool is at RRDtool - RRDtool Documentation
Maybe this explains some aspects of behaviour. If the roadwarrior graphs donāt behave as expected, feel free to show us this differences or raise a bug in BugZilla