The conditions they are kept in and food available at the time have a massive factor in it. However, of all the species I keep these are the longest, the queen will lay in batches too rather than continuously. Could be anything up to few months, when you consider they also hibernate for a good 5 or 6 months you'll soon realise that a small colony will take several years before it starts to get large. I'm in my third year and I'm only now just starting to see the colony expand at a greater rate. The first 2 years will be slow, from my experience and others who have kept them on here don't expect much for a while yet. If you want a fast growing species this is not it. Good luck mine is now about 300-400 strong and she still lays in batches.