Student or Learner
1> I've written quite a few novels during the past seven days.
2> I wrote quite a few novels during the past seven days.
have done+during the past days or did+during the past days?
It is also worth noting that usually the present perfect is used for actions which, although happened in the past, have an important influence in the present. That is one of the reasons it is called present perfect.
But the distinction between simple present and present perfect is not so simple and has been changing recently. It would be good to read a native speaker's opinion about it.
Not a native speaker
I wrote a few novels.
When did you write the novels?
During/over the past seven days --> time stated --> SIMPLE PAST TENSE
not a teacher
Consider these questions:
1. What have you done in the last seven days?
2. What did you do in the last seven days?
Question 1. is more common and traditionally more correct.
If the period of time does not extend to the present, you'd use the simple past:
3. What did you do last week? NOT 4. *What have you done last week?
You might find that Americans prefer the simple past in both cases.
When I wrote that post I stopped for while to think about whether I should use those has's you mentioned. Then I concluded both forms were correct but I decided to use the present perfect because the referred action played an important hole in the present time. And by "to reserve" I tried to mean that the simple past may be used in that case (as opposed to Izicc's example), but I didn't say that you cannot use the present perfect - you may use both.