Different strength/types of beer will condition at different times, conditioning is the time taken for the beer to reach its peak taste/flavour, one rule of thumb is that the higher the ABV then the longer the conditioning time that should be allowed for. You could just keg and carb it the second fermentation has finished but expect a cloudy beer. If you have 6 weeks i would ferment for 3 weeks, rack to another vessel for 1/2 a day and then keg it, a small burst of Co2 to purge the keg then leave it for 2 weeks, the final week i would be force carbing it and chilling, purge excess pressure and serve at 5 psi or thereabouts depending on your setup. As Big C points out about tying up kegs for long periods i should say that i use 3 kegs, 1 for drinking, 1 empty for next batch and 1 for conditioning.