In all fairness, one of the reasons I keep it in one thread is that I often make several releases within the space of a few days; compared to Lix which might have a release every few months usually. Though not cluttering the board too much was my logic behind putting NeoLemmix and NeoLemEdit in the same topic.
There's also that, while some people are finding it fun to play existing levels with NeoLemmix's added features (like gimmick forcing etc), the only content atually being created specifically for it is my own Lemmings Plus III. While that remains the case, a subforum probably isn't nessecary.