Yup - I call one hour my 'magic visiting cube'. I am well past my tolerance and petering out. My doctor said 20 minutes is more like it. He said people with AS (not universal, I know ) tend to have a shot glass to fill for social interactions while NT's have a mug. We fill up faster with a smaller amount.
I think self-awareness helps and just planning your activities as much as possible to allow the necessary down time. I have to do homework and then go to school, so I won;t get to this right now, but you might want to look up Tony Attwood because I believe he says something like for every hour of social interaction allow n-th time solitary. I just skimmed it with the intent to go back and read more ... but yes, it is common.
So, what you are doing, you might make routine. You might say to yourself : I will be tired after this, so I will rest up as much as possible before I go and then go home and have my routine nap ... and then maybe followed by an activity you find relaxing or something. I have spent a lot of time isolating and it does nothing for the anxiety that I suffer as well. Just food for thought.
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Great spirits have always encountered violent opposition from mediocre minds - Albert Einstein.