Newbie - there's a wealth of information on here. You can use the advanced search function by clicking on the little down arrow next to the word search on the links bar above. If you've got time, you will be able to find lots of posts about milts, and there will be quite a lot of information on other people's culture of them, growing conditions and success stories.
I personally haven't had resounding success, but one miltassia I did have had roots everywhere and when I finally got around to repotting, all there was inside the pot was roots - no media whatsoever. I think the poor thing had been starving for quite a while.
If you've got roots growing all over the shop, it may well be time. I am not sure if you are best off repotting milts when they are in active growth, but if it is sort of hibernating, now might be a good time. There are definitely more knowledgeable people than me on here when it comes to milts.
If you do google miltassia culture, you will probably come up with links to this forum!