perfect tense

[navi tasan]

1-I have done a lot of things here for the last three years.
1a-I have done a lot of things here in the last three years.
It seems to me that the meanings of 1 and 1a are different.
To me it seems that in 1, I have been doing a lot of things, while in 1a I can't say that I have been doing a lot of things, because the things might not have been habitual actions. Am I correct?

Can't 1 be replaced with:
2-I have been doing a lot of things here for the last three years.

[Tdol]

1a- This doesn't necessarily cover the whole period of tim e- i could have been in and out.
2- Yes