All the time
I consider hyper-focus and obsession among the perks of aspergers!
When I get into a special project, either through work or at home, then I work on it ALL THE TIME. Sometimes day and night, weekends, during lunch, every waking minute. I've had many special projects, the work ones have served me well financially and the home ones I have enjoyed. I once had post natal depression and so became obsessed with neuroscience. I really enjoyed that.
And they might be right about burn out, I've burned out at least 5 times. I just deal with it when it comes up now. When it starts, I now recognize the symptoms, which for me is constant fatigue, irritability, tachycardia and uncharacteristic emotion turns, lots of tears. When it happens then I try to sleep more, exercise, eat healthy and throw myself into a computer game. After a few months I bounce back stronger and resume whatever research I was conducting.
I sometimes try to "switch off", but it is still forced. I put on really BIG headphones and read a book, or watch a marvel film or play a computer game. But it is still an effort and my version of "switching off" is very different to everyone I know. I can't sit in a bar with a drink and I can't watch soap operas or sports. Even my "switching off" is focused and deliberate.
So I wouldn't worry about what other people think you
should be doing, thank them for caring, tell them you appreciate their concern and have taken their opinions on board, smile and nod, and figure out what works for you.