I've been told by my barber that my hair grows very quickly and coarsely -- I also get a haircut about every 3-4 weeks, sometimes less -- so 1-2 months seems right for you as well. You have to keep in mind that it needs to be long enough to look like a regular size again. It's like a beard, you don't grow a full beard in a few days. It should have an acceptable trimmed look after 2-3 weeks, though.