Depending on the style and original gravity of your beer, I would always let it condition in the primary on top of the yeast cake without racking it to a secondary. Racking to a secondary, IMO, is not necessary whatsoever unless you are working with fruit, hop, oak, wild yeast/bacteria, or spice additions. Let your beer stay on the yeast cake for a minimum of 2 wks to properly condition (once again, this is gravity/style dependent) prior to racking to a purged keg and carbonating for serving. Once the beer is in the keg, it can be aged as long as needed to allow the beer to come into its own.