The history is what's important for me most often, to build a baseline so to speak. Therefore for me it would be on all the time.
Smokeping just uses RRDs with RRDTool so it's super simple and really fast, even with a significant amount of history. I'd hate to see the additional load of 1000's of pings and all the associated telemetry being stored in mssql... but I'm no DBA so I can only imagine.