They can be quite different between airlines, both in the amount of time and the amount of stuff to learn even between airlines in the same regulatory area. A friend of mine had one lasting roughly half a year, my first one in a previous airline was around 3 months and in my current airline it is around 3 to 4 weeks. Quite often a command is coming with a change of type, therefore a full type rating has to be included in the course, but even if you are not changing types there are big differences between airlines. Best to check your training manual about it.