Even though I am not DID, I do have some experience with a good friend who is DID. And yes, everyone's system and how it works can be very different. There is no "wrong way" for a system to work. Comparisons are fine to make as an informational way of getting to know someone but no one should ever feel that their system, because it works differently is wrong.
In gaining co-consciousness for my friend, she is able to ask her alters to do things for her, like walking up stairs. There are a couple who are fit and strong and do not suffer from the physical ailments that my friend has. So when she has to carry something upstairs or she is in a lot of physical pain, she can ask them for help and they step up to help her.
She also has littles that like to come out and play or watch a movie. Unless she is severely triggered, she has the control now to either allow them to come out or not allow them to come out. They found out that when I was a kid I got a spirograph for Christmas one year. This year, they got me an really cool spirograph for Christmas and they can't wait to come out and learn how to use it. I know we'll have a great time playing with it!
And then, there are times when my friend switches and has no idea except that she lost time. Mostly it happens when she's getting a bad memory or there is an anniversary of sorts. It's happened less and less over the years as she has gained more co-consciousness with more in her system.
I just wanted to chime in so that ya'll could see that there are times when a DID'er can allow an alter to come out and her step back. Most of the time now when that happens she is able to listen to what is being said, providing the alter doesn't have a problem with that.

to all!