I just did an SR series and 2 extra 200s this season - I've come to think that with a basic level of conditioning and aerobic fitness, audaxes (for me anyway) are a kind of de-training as they pile on fatigue without much training benefit, and the recovery needed robs time from more productive training that could have been done instead. I did quite a lot of distance (9,000km) before LEL and don't think it stood me in particularly good stead - I wanted to be quicker.
I have 7,500km this year since Jan, but what's different this season is I've been more consistently on the turbo (85 hours) ... according to veloviewer I've had more time "in the red" than in any preceding year. Being on the turbo more in winter has also helped me avoid a crash on ice - something which put a crimp in a couple of previous seasons.
I also did a Raid Pyrénéen (plug: write-up
here) last month, partly as PBP-prep. As a Cambridge-based flatlander I though I needed some verticality in the legs, in readiness for the PBP rolling terrain.
As a PBP newbie, I'll be interested to see how this all works out!