QUOTE (bayonet @ Nov 16 2008, 11:00 PM)

in my opinion, never being bothered by the use of "了". The function of it is to indicate a perfective tense. U could use it with another functional word like "已经'' (already) or use it alone. But the confusing part is many people have found that the use of "了" is beyond that function and being seen in many other occasions. This is because it is used in a very casual way which in many cases it has no or very little significance at all. people use it simple because it has a descending tone which would make the sentence sound completed. So use it whenever u want to use it
I am afraid it is not wrong. Despite a bit wordy i.e. use 了 twice the grammar is perfectly right. The sentence means two years ago,i had (already) lived in beijing for 8 months. In some cases, in an implied way, 已经 could mean something that u still doing it, but it is very ambiguous. Without a certain context, people usually would not notice it.
The use of (曾经) is not necessary in my opinion. Of course it is not wrong if u use it and will be more precisely to express that" u no longer being there after living for two years".
i dont know where u learnt that from. I guess this is designed for english speaking people as u can match them with the tenses in english gramma, hence easier to understand. Since there are no structures in Chinese as " have been doing..." or "had been doing..." , this way of explaination is smart. But usually chinese people would not notice the implied difference between "已经"and"曾经", so if u want to precisely express what u mean u might need a few more functional words. i d like to rearrange it in this way, 我学过两年中文(i ve studied chinese for 2 years), 我以前or曾经学过两年中文(i had studied chinese for 2 years), 到现在我学中文已经两年了or到现在我中文已经学了两年了or到现在我已经学了两年中文了or我学中文到现在已经两年了or我到现在学中文已经两年了(they all mean i ve been studying chinese for 2 years, it is quite flexible to put the functional words in the sentence. 到现在means till now, i put it here to indicate the verb is continuing from a time point in the past till now. This is totally unnecessary in the" have been doing" structure in english, but for chinese as said above there is no such a structure, it will be necessary to strengthen the implied meaning of " 已经")
I'm portuguese!!
And i'm studying chinese for only 2 years.
I've started the 3 year about a monht.
Your exapmples are really good,but there's a diference if you use
已经 or 曾经 with 了。And 了 not always refers to past.
Notice:
昨天我问了他。yesterday i've hasked him.(past)
我到了,但他还没有到。i've already arrived,but he didn't.(still not arrive
but it'll come).(present)
我想去了北京后,再去上海。I'm thinking going to shanghai,after going to
beijing.(future.)
他已经去中国了。He already left to china.
他已经去过中国了。He has been in china.
他曾经去过中国。He has been in china.
This are some examples why 了 can confuse a lot of us.