Page 101 - Practical English Usage 3ed - Michael Swan, Oxford

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They can also be used to talk about things which we know are not true.
I feel as ipthough I'm dying.
She was acting as iflthough she was in charge.
tenses
When we talk about things which we know are not true, we can use a past tense with a present meaning after as if!though. This emphasises the meaning of unreality. Compare:
- She looks as ifshe is rich. (Perhaps she is.)
He talks as if he was rich. (But he is definitely not.)
- You look as though you know each other.
Why is he looking at me as though he knew me? I've never seen him before. In a formal style, were can be used instead of was in an 'unreal' comparison. This is common in American English.
He talks as ifhe were rich.
like meaning 'as if/though'
Like is often used in the same way as as if/though, especially in an informal style. This used to be typically ArnE, but it is now common in BrE.
It seems like it's going to rain.
He sat there smiling like it was his birthday.
For the difference between like and as, see 326.
as long as tenses
After as long as, we use a present tense to express a future idea.
I'll remember that day as long as I live. (NOT ••• tiS 18ttg tiS Il:tJilllive.)
For other conjunctions which are used in this way, see 580.
conditions
As!so long as is often used to state conditions.
You can take my car as!so long as you drive carefully.
(= ... on condition that you drive carefully.) emphatic use
Before a number, as long as can be used to suggest great length. These meetings can last as long as four hours.
For a similar use of as muchlmany as, see 136.6
as such
Not . .. as such is used to say that something is not exactly what has been suggested.
So you went to Japan on holiday?~ Well, not a holiday as such - I went on business. But I managed quite a lot ofsightseeing.
I'm not a teacher as such, but I've taught English to some of my friends. ~ page 69
as such 76