This is mostly how I operate, too.
Keep it in FLAC so I always have something to go back to.
But if I ever need a USB stick to play in the car, I'm just going MP3 and not thinking twice about it.
I know every car that plays from USB is going to play MP3 just fine.
flac is my standard go to anyway. If I need to move music to a more limited storage medium, flac->mp3 is where it's at.
This is mostly how I operate, too. Keep it in FLAC so I always have something to go back to.
But if I ever need a USB stick to play in the car, I'm just going MP3 and not thinking twice about it. I know every car that plays from USB is going to play MP3 just fine.