I am a purely Offline Singleplayer myself Munginho. No you are not doing anything wrong friend. They simply take a LONG time to spawn in on Singleplayer mode, up to 1.5 hours! But just checking Munginho, are you certain you are in the correct area? I have examined this issue in fairly good detail in a seperate thread which I created here (see below). If you have any questions, shoot.