It takes me by surprise, frequently.
Sometimes she speaks to acquaintances (neighbors, local friends) and I open my mouth to translate exactly as they open their mouth to respond to her, not needing my translation because they understood her just fine.
Other times (like in the video below) people (including me) think they understand, and respond as if they understand, and the conversation turns away from her message, and she often doesn't fight back to correct it.
Sometimes she is so tired in the afternoon, or when she isn't feeling well, or when she gets too hot or too cold or is somehow off-kilter, and she is silent again. She'll use Mini then, if I bring it to her and sit quietly with her and we take turns tapping things . . . but the quiet, the almost total lack of speech . . . it surprises me, too. Just as much as the talkative times do.
Once upon a time, we fit so clearly into the second A of AAC (augmentative and alternative communication)---her talker was an alternative form of communication, since speech wasn't accessible. Now we straddle the augmentative and alternative worlds---sometimes our device augments speech, sometimes it's an alternate method of communication, and sometimes we have to go and search for it because we haven't used it in hours (whoops).
The video below, in which Maya describes some drama from her bus ride home, is a snapshot of Maya's speech right now. The fact that it includes me responding incorrectly to something she says also shows how important AAC is for people who don't have reliably intelligible speech---she needs a way of clarifying what she says and she also needs a reliable communication method to use with people who won't understand her speech (or when her speech is difficult to access, like when she's tired). Because of this need for AAC, it's important that we keep modeling, so that she keeps her skills up to par, learns where new words are, doesn't forget the locations of other words, etc. It's much easier to drop the modeling ball when Maya herself is favoring speech---but we can't let ourselves off the hook, not if we want her AAC vocabulary to stay solid (and expand!).