A further thought, not related directly to the OP, but nevertheless, bar bags do play a role.
As distances get longer, your intensity increases, or the weather deteriorates, tiredness can play some wicked tricks on riders and their memories. Being well organised is a key.
In other words, having a stash for a group of items, such as tools and tubes, small clothing, energy food, car keys, spare lighting, and knowing where those stashes are on your bike will become vital when tiredness sets in and the hallucinations start.
I am always paranoid about losing my brevet card (even more so now that it has happened on a populaire recently), and knowing where that is at all times is paramount. Of course, it could be a jersey pocket, but sweat and rain can play havoc with the card, and a zipseal bag can become clammy.
You have to ride with the same sort of stashes as often as you can, even in training or on short randonnees. Coming back to riding in recent times with a new bike and equipment has meant I have had to relearn some of these things, but by the time a 1000 or PBP comes around, I should know exactly where everything is...