After I made a paper wallet for long-term saving,
I start thinking about posibility that somone can create same priv. key
in their wallet in the future.
I know that posibility for this is very small, but it exist.
If someone want to create billions and billions private keys,
he can generate someone address with positive balance.
What you people think about that? This can become a big problem
for Bitcoin in the future... no?
I am a little scared

Its very small, but i cant describe how small it is, higher odds for you to being hit by a bus then to that happen.
Its also more likely to be hit by a meteorite than for that to happen, so better buy insurance agains meteorite hits than agains duplicate priv key.