AT&T Data Plan Change a Good Idea?

A couple of months ago I switched our AT&T unlimited data plan to a reduced plan for a lower cost every month. The main reasons were to have Mifi, and after evaluating the amount of data we traditionally use, we never really used a lot - until recently. I needed to Mifi because whenever we travel, and I have digital art work to do and need to communicate with my customers. Using an iPhone is too small and I need access to everything on my iPad. My iPad is only Wifi enabled and does not have a cellular option. However, whenever we travel, and I use google maps, the data usage spikes. AT&T is very good about warning us about the per cent data that has been used, and we do everything we can to minimize using any more. But it just doesn't seem to help. So I was a bit surprised when we received a notice that we would get a $30 credit related to the overage charges last month. After all, we have been their customers forever, and I also have an automatic data plan set up on my mom's iPad because she has no wifi in her house. I'm beginning to wonder if changing the plan was a good idea. It is a lot less per month, and these occasional overages are tolerable - but certainly not appreciated one bit. I'll take the credit for last month but I have a feeling we'll never see it again.