I'm with Newton and likewise I have acess 24/7. Although I can trade commission free there is still the spread which is in the 0.75% area. Also the trades are in $Cad so I eat the spread there also. I can move my BTC to a cold wallet so if I ever accumulate a significant amount I'll be doing that.
-----
I've had better and worse than that but on an average 25% is close. I spend a lot of what I make but a chart of my liquid networth climbs steadily without too much drawdown.
-------
I never heard of Newton. I also did not hear of Quadriga before it got hacked and shutdown...
When Cryptsy/Mintpal shutdown, I lost a few hundred $ worth of XMY because there were not many exchanges for Myriadcoin had left them there. Not my keys, not my coins
When Cryptopia shutdown, I lost maybe less than $10 worth of cryptos there. Not my keys, not my coins
Today, I have 1.5 BTC at Coinbase and Kraken, each. I divided the 3 BTC, by withdrawing 1.5 btc from Coinbase to local wallet then to Krakan, in multiple transfers, total cost of all transfers added to less than $1
Now, I doubled the surface risk of loss from an exchange shutting down (either Kraken or Coinbase) but lowered the risk of loss amount for each occurrence
---------
I have a slight OCD and noticed $500K you were referring to was different than $500K+ I was referring to. Anyway, I cashed out over $700K, and the cash is not gone even after paying taxes and all living expenses for over a year.
No house, no debt, Tesla is bought and paid for all cash so cash burn rate is not too high (all relative, of course, cannot compare to countries of lower cost of living)