Wow, I post one thing and in two days this happens.
I love the internet.
And leeches can last ten years. My friend owns a farm and haschickens he cuts up, otherwise leech food.
Most leeches don't suck blood. They eat fish and pond scum, and will eat eggs if you put one with them.
The reason I want leeches is to do experiments. And torture people. that too.
Does this explain it?
That should answer your questions.