Sounds like you could be doing a bit too much, to me at least. I tend to hold 'long-distance conditioning' with a long ride once a fortnight, possibly stretching to once a month if I have short fast rides in-between.

Really, a brevet consists of a series of 60-80 km rides between checkpoints. It doesn't sound like you'd be too concerned about riding 60-80 km.

I did my first PBP (<70 hr) on commuting 110 km round trip up to twice a week, some brevets and usually a 40 km Sunday morning ride. My second (<82 hr but more sleep and chatting) was virtually no mid-week riding and riding most weekends, from 20 km trundles to a fair few brevets.

In general, provided you are comfortable on the bike (no aches) and confident that you will finish even if conditions are not perfect, rides don't get much harder as they get longer (400s aren't too much easier than 1000s). Americans seem to 'race' brevets more than most. I think that approach would grind me down on repeated longer rides.

Only you know how you feel though.