How have your beers turned out when you add the extras? This is something that I have tried with a semi-success....
I also use kits and tried boiling up my water with a variety of spices (cinamon, mixed spices etc) in a large cotton teabag like way. Once the water had cooled, I added this to the wort. Once the beer was ready to drink it tasted fantastic and really christmasy, justthe way that I wanted.
WHile over the last couple of months I have been 'sampling' this beer (over half the batch gone now) I have noticed that the great taste of christmas appears to be dissappearing :( Although I haven't tasted any for about 3 weeks now, I do know that it will no longer have any of the fantastic flavour thatI brewed it for :(
How have you added the extras and have the flavours lasted at all?
I did have the same problem with a stout, except in this instance, when kegging, along with the priming sugar, I poured in a bottle of Ginger Wine. Again for the first couple of weeks this had a fantastic ginger flavour to it which slowly faded over time. The only thing that has had any lasting effect was a stoutt hat I added a few pots of freshly brewed coffee.....