I've put a BIP-38 encrypted key on a pendant when my niece was born 6 years ago with 0.1 on it. Me and my sister have backups and I put €20 on there every month (manually). There is some platforms that allow for automated monthly buys but you still need to withdraw from them so you might as well do it yourself whenever you buy some corn. 

 20 bucks a month? What about fees? 

 I transfer when the mempool complies. Like today. 

 Fuckin Legend 🫡

I just stumbled upon 21bitcoin. Seems they have an auto withdraw feature when a certain threshold is reached. Sounds interesting..🤔