since without perfect tense in the main clause

Question

According to Michael Swan's Practical English Usage, it is possible to use since without perfect tenses in the main clause, especially in sentences about change. The examples given are:

1. You're looking much better since your operation.

2. She doesn't come round to see us so much since her marriage.

3. Since last Sunday I can't stop thinking about you.

4. Things weren't going so well since Father's illness.

I'm unable to understand this rule well enough. What about these sentences:

• I'm living at my friend's house since last Sunday. (= I lived somewhere else before Sunday but now I live with my friend, which is a change).

• Since coming to London, I play a lot of Cricket (I didn't play much Cricket before coming to London but now I play a lot).

• I know her since last year (I didn't know her before last year but now I do).*

Are these sentences also correct?

Answer 1

Of your suggestions, I think only the second is both grammatically valid and natural.

"I'm living" is the present tense, but that doesn't work well with "since". I think this should be:

I have been living at my friend's house since last Sunday.

"I know her" similarly does not work with since. I think this should be:

I have known her since last year.

I find it hard to formulate a general rule that covers all these examples.