Never Come Down

I have branches, but no fruit, trunk or leaves. 

What am I?

How many seconds are there in one year?

Guess what comes next in the sequence:

1 2 3 4 5 ? 

The answer is not 6. What is the answer?

When you want to use me, you throw me away. 

When you're done using me, you bring me in. 

What am I?