First of all... I like this piece, its minimal concept (I make music like this too...)
...but it's like Farstom said. For a track that long there need to be more variation in your sounds... or shifting of sounds (while keeping the melodic concept). What I also miss a little is a story that's told... meaning track structure... intro... main part... break... main part variation... and so on. (I hope you know what I mean)