You current points are based on activities over the past 12 months: points that are 12 months old are removed. Your lifetime points continues to increase, unless content is deleted: http://scn.sap.com/people/v.satya/reputation This has been covered several times on other threads if you would like a more in depth explanation.
A new version of the reputation system is coming online soon: Game On! #Gamification Coming to #SCN (SAP Community Network)