Yeah it could find a valid block hash anytime between right now and 4000 years from now lol.
$168k per block is just counting the block subsidy. Fees add more, especially lately.
I'm only running one but I'm going to buy more until I have all the USB ports on that hub occupied. 7 ports, so six miners and one USB powered fan.
These things only pull a few watts, so the electricity cost is negligible. Less power than leaving an LED light bulb turned on.