So, as I’ve done for decades now,
hi there
whats meaning of this sentence?So, as I’ve done for decades now, and meaning "left"

He said he plans to spend the time that he has
left writing, being with friends, not doing interviews. But he did agree to share
his thoughts exclusively with us tonight, for you gathered here, because he’s
one of our family. So, as I’ve done for decades now, I went over to his house
in Manhattan with my mic, and I said to him …

Question

So, as I’ve done for decades now,
hi there
whats meaning of  this sentence?So, as I’ve done for decades now, and meaning "left"

He said he plans to spend the time that he has
left writing, being with friends, not doing interviews. But he did agree to share
his thoughts exclusively with us tonight, for you gathered here, because he’s
one of our family. So, as I’ve done for decades now, I went over to his house
in Manhattan with my mic, and I said to him …

Answer

"a decade" means 10 years. So "decades" mean many periods of 10 years; it is not specified how many.
"I've done for" indicated Present Perfect tense which is used when something began in the past but continues until now. For example, I started studying psychology in 2011 and I am still doing it so I would say "I HAVE STUDIED psychology FOR 9 years.
Summing up, "I've done (it) for decades" means that I started doing something many years ago (more than 10) and I am still doing it.

"Left" in this context refers to free time that he had. For example, I should be at a meeting from 1 to 2 pm but the meeting ended at 1.45pm, so I can say "I spend 15 minutes that were LEFT eating my lunch".

If you have more questions or you want to work on your English, please feel free to contact me.

Answer

'do' in this sense is habitual.  Do you wake early? I do, I have done so for as long as I can remember.  It is time to have done with this topic!

Answer

oops! Sorry, I posted my answer twice so I removed the one here. See the answer below.