Bottle-Ageing Porter

I made a batch of porter recently (OG 1.051, FG 1.011) and have kegged half and bottled half. I have been told a few times that porter tastes better after it has conditioned for a month or so. I hope so, because on my kegged half (it has carbonated now), I get a taste which I can only describe as a bit like saccharin on the aftertaste (ie a little bit of a synthetic aftertaste). The aroma is good, the slightly toasty flavour is all there, but there is just a slightly odd aftertaste. Does this soften out and eventually go away, or do you think it is perhaps due to my CO2 carbonation?