Depends what you're after. To me the 400 was a good day (and night) out, passing through fantastic scenery. The stops are part of that day out. I like a good scoff now and again. I also like taking a few pics, and probably spent 20 mins or so just asking pics from the Severn Crossing bridge. I also took some around Symonds Yat.
As long as I'm not pushing time limits, and have time for my stops, I'm more than happy. I'm also noting that my moving average, and percentage time stopped are not changing much from 100,200,300, to 400 which is a good indicator I'm getting it right (for me). Got my first 600 in 3 weeks, so well see how the stats work out then.
Besides, after my red bull around midnight, I was wired for the section through the Chilterns and I quite enjoyed that. There was something reassuring seeing places I'm familiar with and realising barring anything major I was going to complete my first 400 in good form.