As a newbie I spent some time online trying to learn what I needed to know about bitcoins.
Naturally, people are concerned about security.  I found advice such as:
never store your bitcoins on a computer that is online
never write down keys, they could be read or stolen by others
never put keys on anything you could lose, such as usb drives etc.
All this makes sense and would appear to be sound.
However, it all leaves me wondering what happens to my bitcoins when I eventually pop my clogs.
Obviously it isn't safe to write down keys in your will.
If I gave a key to our daughter, she would either lose it, forget it, or abuse it.
So how would you leave your bitcoins to someone in your will?  There doesn't seem to be any way of doing this.
It follows from all this that when you die, your bitcoins die with you.
I have read that when bitcoins are lost, there is no way of retrieving them.  It's not as if someone could find them buried in a field in 50 years time.
Given that bitcoins will inevitably be lost for various reasons, it follows that the total number of bitcoins will decline steadily.  Given enough time, maybe they will all be lost................?
What do others think?

Thanks everyone for your comment. 
Some of them were very helpful.

In April this year I made a tentative start in Bitcoins.
I set up the software, and waited for it to sync....  and found it had used up all my internet traffic quota.
So I reduced maxconnections, then to gain confidence I went to 2 faucets and signed up for small contributions.  I sent each one a new address so I knew what had come from whom.
The faucets were:
daily bitcoins.org
bitcoinfaucet.at
I waited and waited, expecting something small to appear.  Still nothing, after 2 days!
So I tried 3 more:
freenitcoins.macdonaldboats.com
coinreaper.com
cointicket.org
Still nothing, after a week!
Where did I go wrong?  Can anyone help please?