Present Perfect

Hi teachers,

1. He has worked in this company for sixteen years.
The sentence tells us what has happened (He has worked in this company), and the period of time (sixteen years).

2. I have painted two rooms since lunchtime.
The sentence tells us what happened (I painted two rooms), and the period of time (since lunchtime).

The present perfect does not in itself say whether or not it has finished or not finished, but the context tells if it has finished or still continues.

My question:
That said, according to both examples above, does this guideline make sense?
When we use the present perfect with the prepositions "since or "for", we are thinking about (1) actions or events in progress for a period of time until now or (2) actions that were in progress for a period of time until now.

I'm not sure about the guideline number (2) according to the example "I have painted two rooms since lunchtime".

Thanks for your help.