Flashing white front and rear red on the road ALL THE TIME. I've worn hi-vis vests for years. Sure, they HELP, but they're nothing like a flashing light. I won't ride without 'em anymore.

One might argue solid might reduce annoyance to other road users, but this is peripheral. If drivers are so "concerned" about flashing lights "hurting their sensitive eyes," then perhaps they should STOP MOWING PEOPLE DOWN! If they didn't behave so egregiously behind the wheel, perhaps we wouldn't need lights! And if our transportation infrastructure supported safe cycling more, then ok.

Two experiences after 40 years of urban commuting convinced me to use lights 24/7:
1) Driving Mt. Hamilton in the sports car. Love seeing the cyclists out and about on the mountain. I noticed that the frequent light-shade transitions make it challenging to see a cyclist who just entered the shade. My eyes are pretty good still, so I think it's just normal for someone's eyes to take a moment to adjust. (And yes, I understand that if when I'm driving, I can't "see" what's up ahead, it's my responsibility to slow down or stop. The old, "The sun was in my eyes!" excuse is lame.) Well, the cyclists using lights? CLEAR AS DAY. There was and is never an issue of seeing them when they just entered a shady spot of road. This alone convinced me that I should be riding with daytime lights.
2) Getting hit by a moron. Now I readily admit that this moron probably wouldn't have noticed my light and hit me anyway. But while riding during Covid next to a VERY busy park with bumper-to-bumper traffic, I feel having lights would have elevated my visibility and presence within the roadscape, making a collision far less likely. Luckily it was only a glancing blow, I didn't go down and the bike was undamaged. My left knee was sore for the next few days though. After stopping, the driver quietly drove away, avoiding any responsibility. Pissed me off.

And since motorcycles are now mandated to have headlights today, it only makes sense for cyclists to use lights during the day.

We're simply too vulnerable in the American transportation landscape to just assume we'll be seen without a little something more.

And should they flash? I get the debate. I assume flashing was always a preferred option to extend run times and battery life. Today's LEDs are so much more efficient, that this benefit isn't as crucial as it used to be 20+ years ago.