I have had Gastropresis for about 8 years and it has varied from mild to severe. There have been long periods of time where I've been well (like a year without major incident). Then I've eventually gotten sick again with another GP episode later. I think it has a lot to do with the unpredictability of digestion with GP. Sometimes your digestion can be normal for a period of time and then very delayed at other times. How well you control your bloodsugars also plays a large part in how severe your GP is. In my experience stress and the amount of rest/sleep I get affects my GP as well.
As far as appetite, yes I've had an increase in appetite since I've been well too. I have another theory about this though that many other people with GP may be able to relate to. If you've been majorly sick from GP for a long period of time, you know how it feels to go through not being able to eat anything for several days at a time. I think, at least in my case, that when you go through this, your body and mind may feel the need to eat more while you are able to do so (while you are feeling well). Think of what a bear does to prepare for hibernation. It eats more to withstand the long period of time that it knows it won't be able to eat. Although not an exact comparison, you can see how in some ways it makes sense.
I'm glad that your GP is doing better as a result of you improved bloodsugar control. You should keep in mind the stress/rest/sleep factor that I mentioned too that can affect your GP. I almost forgot, getting sick with a virus or other ailment can also make you have a GP episode. So trying to stay well overall will help too.