Yes, that is the idea. Accumulate the most Bitcoin I can, while I'm alive. Then, someone will have to take over. And I'm in Bitcoin since late 2018, so, I'm aware of most good practices when it comes to safety such as the fact you mention about keys and non-custodial wallets! I'm kinda old school and usually I do my transactions by hand. And I have my own plan to save my PKs, so, I think I'm more or less safe regarding safety!
Since Bitcoin still in downtrend its very good ideas keep accumulate as how much bitcoin you can, I have adopted this your ideas when spending few percent of my salary and invested in Bitcoin regarding price still drop based on
ALL TIME HIGH of Bitcoin price. Its not matter where are the place for saving Bitcoin fund but you look as long term investment and worth when holding in non-custodial wallets, but my Bitcoin accumulate in daily day too small and I used exchange market to make easy when transaction or purchasing fund to buy Bitcoin, but we have the same target holding as long possible and selling Bitcoin with another all time high at the future.
I have target in next few months later my salary grow up and get higher chance for accumulated bitcoin with bigger fund, right now spent about 20$ to $30 in daily day for accumulating bitcoin as my investment assets for the future.
I'm not sure I understood. You are using exchanges to buy Bitcoin, right? Well, my only advice is that you take that Bitcoin out of the exchange regularly. Don't accumulate too much in any exchange. Also, if you learn how to do it on your own, is a learning curve that pays out in the future. And it's always grateful to know more and more about Bitcoin and all the system around it!
And if you're spending $20 to $30 daily, that's very very good amount at the end of the month. I cannot buy that much. But it doesn't matter. Each one of us buy what we can buy! That's all we need!