Hi, I'm interested in buying some crypto and I've thought about storing it on paper wallets. Mostly BTC & ETH.
I have 8 different places to store it in so fire/water damage won't be an issue.
I'm just wondering about why I'd need to sweep the whole wallet when sending the btc? From what I understand you basically have a private and public keypair and the private is used for signing payments. I'll encrypt the printed keys with a 30-character password which I remember and only store in my brain (permutation of my master password for everything SUPER important, used similar twice before).

Of course I should discard my wallet if I use it on something like a 24/7 networked Windows machine but I guess my airgapped (except when I send payment) FreeBSD laptop would be fine? I'll only use it for crypto payments. The method of sending will be geth (Ether) and my own tool written in BitcoinJ or btcd for Bitcoin. I'm not worried about being tracked either at all because I'll use this only for hodling/some legit payments.

What I'm asking about is why I should recreate a wallet immediately after making a payment? Seems overkill as long as I use a safe computer.
I'll also only store the private key in a ramdisk so any forensic analysis will be useless.

I'll start pretty small at around $1000 since I'm a student, and I rather not risk more. A hardware based solution seems ok but if it costs 10% of what my total amount is it seems like a waste.

So, what's the point of sweeping?
Example for Ethereum:
1. Store private key in ramdisk & use personal.importRawKey to import it after inputting manually from paper (configured geth to store everything in ramdisk ofc).
2. unlock my account with personal.unlockAccount.
3. send eth with eth.sendTransaction.
4. shut down the computer.
Is there any flaw here that I'm missing? I'll get addresses, gas prices, etc. from another computer because I don't want any web browsers installed on the computer.
I'll use the same principles when sending Bitcoin, any recommendations for simple free software Bitcoin tools like geth? I know how to write my own in BitcoinJ but I'd rather want a stable fool-proof one tbh.