Can I get them back even after not being online for 30 years or so (Assuming I'm still alive by then..)?
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That's right, they are stored in the blockchain. Bitcoins does not actually exist anywhere, the blockchain is just a bunch of transactions, starting with a generation transaction with just a receiver and no sender. Your wallet file only contain the private keys needed to sign a transaction from the corresponding bitcoin address.
I suggest reading the Bitcoin white paper by Satoshi Nakamoto, the wiki and, if you'll understand it, the source code. Links at bitcoin.org.