'Temporal Autism'

Most things I've heard and read speak of autism as a set thing - with certain innate characteristics, bio-neurological dispositions, and behavioural traits etc, whereby they're almost spoken about as a definite and concrete phenomenon.

However, my personal experience of autism is that it feels much more plastic and organic - as certain traits have seemed to change over time, and others have seemingly gotten worse with age. For example: as I'm getting older, I find my thinking is notably much more rigid and inflexible than it used to be. So, should I be actively expecting my autistic characteristics to change with age? Or, are the underlying mechanisms still the same, just my relationship (perception?) to it that's changing over time?

Does anyone else have experience of autism being more 'fluid' and organic than is often communicated?

Does anyone know of any books or articles that explore this aspect of autism (e.g. longitudinal / lifespan studies etc)?