A number of direct mail practitioners - including myself - have found that up to a third of your total orders come in the first week.
If you had 1 order, you could probably expect a total of 3 from that ad. This industry sales percentage appears to be consistent enough to predict your total sales. So, yes, maybe you do need to change your approach right now.
How can you improve it? The conversion percentage will depend on a number of factors, but the most powerful is a time-sensitive offer. If you don't have one in your information pack offer, then most of your sales potential is lost, because people are inherently lazy and won't do anything until they perceive they're missing out. Obvious I know, but backed up time and time again in my experience.