I've only done Ride London 86. I stopped twice, first one was to attempt to drain out my gloves, I stopped long enough to eat a couple of things (I can't eat on the bike very well so don't try) and was probably intended to be 5 minutes but ended up as 10. The second was probably 20 miles from the finish, I tried to use the mechanic for a minor mechanical but it was all a bit of a waste of time (literally, probably 15 minutes) and I then used around 10 minutes eating (because it was separate to the tools area) and texting the wife) I was grumpy about the length of that stop but at least the rain had stopped. Ride London had huge stops so there was no queuing anywhere when I was there, although I didn't do top of Newlands Corner because it had a reputation for being the primary stop and very busy. I don't do comfort breaks often when riding and didn't need one at either, it all comes out as sweat I think. I was riding 'alone'.
If you aren't disciplined at it, expecting to stop for 5 will turn in to 10 quite easily, but unless you are chasing the cut off, or looking for a great time it really doesn't matter. I used to ride long distance motorbike rallies so am a bit weird about stopping (I hate doing it basically, the stuff I ended up doing had a mandatory rule of no more than 400 miles between stops) so will do it as little as possible, even on a bike.