He has found his keys again since he came home.
He has written another poem since he came home.
Because 'found' and 'written' are 'accomplishment' and 'achievement' respectively , they cannot be used with 'ever since' but can be with 'since'.
From What's the difference Nuance between Ever Since and Since
Since that day, he has become a different person.
With "since", and no "ever", I can write a sentence that implies that he has changed somehow between then and now, but I don't say when. He could have changed three days after "that day", or it could have been yesterday. (This sentence also implies that the change happened because of some reason unrelated to "that day".)
In the case of sentence above, when an achievement verb is used with 'since',does this mean the interval between 'then' and 'now' is extremly small like the effect of 'recently'?