it will take as much time as Thai official takes, you can't predict, just have patience, if they approve you should be able to get the visa by email.....
How long is too long for you? 2 week or 3 week or 4 week? this is not just for you but for anyone who wants to apply for DTV or any visa, have some patience and plan accordingly.....do not take thailand for granted and think they are just waiting for us.