Present Perfect

[henryh]

I often here people say something that contradicts the rules I was taught back at school:

It's been long since I've seen my parents.

I thought I should say: It's been long since I last saw my parents. or It is ages since I saw my parents.

But defenitely not present perfect after 'since'.

So why is that so?
Thx

[Clare James]

The sentence you quote, 'It's been long since I've seen my parents' is not one you'd hear many native speakers say. It's not grammatically correct - the form, as you rightly say should be either 'It's been a long time since I last saw my parents', or 'I haven't seen my parents for ages.'

But, there again, native speakers of English do sometimes make grammatical mistakes!