Even if you can live to be 80 years old, you are not suitable to travel around looking for vampires before you are 20 years old.
When you reach the age of 30, your soul will be tired, and you will want to find a woman and start living a stable life.
Then you only have 10 years to find the vampires.
If you haven't met a vampire in 10 years, then you basically have no hope of continuing this process.
Once you accept becoming a vampire, you give up the whole world.
And the new world you get may not be suitable for you.