[Grammar] have written essays or have been writing essays

[brianbrian]

I would like to make up eight similar sentences below.

(1) Over the last three years, I have written fifty essays.
(2) Over the last three years, I have been writing fifty essays.

(3) Over the last three years, I have written fifty essays in total.
(4) Over the last three years, I have been writing fifty essays in total.

(5) Over the last three years, I have written three essays per month.
(6) Over the last three years, I have been writing three essays per month.

(7) Over the last three years, I have written a lot of essays.
(8) Over the last three years, I have been writing a lot of essays.

I have read a lot of grammar books which seem to say that the present perfect and the present perfect continuous tenses are very similar. I am very confused about them and not sure which one to use in my sentences. Please help me. Thank you very much.

 

[emsr2d2]

1, 3, 5 and 7 make it clear that you have finished all the essays mentioned.
In 2, 4, 6 and 8, it's possible that you're still in the process of writing them all.

 

[Tdol]

2 & 4 are not very likely as sentences because the essays are written in a sequence, not simultaneously.