Audax rides

For a BRM, the time is going to be about 26 hours for 15kph minimum average speed. Non BRM can, I think, be as low as 32 hours at 12.5kph minimum average speed.

BRM limits are based on 15kph of the base distance (i.e. 300km for a 307km ride). You don't get any extra time for the slight bit of overdistance on a BRM. There are two exceptions to the flat 15kph rule; 200km rides are defined as 13h30m and 400km rides have a 27h timelimit. No idea why, but it comes from ACP. So:-

BRM 200: 13h30
BRM 300: 20h
BRM 400: 27h
BRM 600: 40h
BRM 1000: 75h and a bit (it drops to 13.3kph above 700km)
BRM 1200: 90h
1300km to 1899km: 12kph (so 1400km of LEL gives 116h40)
1900km to 2499km: 10kph
2500km+: 200km per day

BR rides (i.e. still Randonnees but not validated by ACP or LRM, only by AUK) can have a 14.3kph minimum average speed (up to 700km where it follows the same minimum average speed as BRM). So that gives near enough 14h for a 200km ride and 28h for a 400km ride, but the overdistance portion counts too, so a 405km BR ride will have 20 odd minutes more time than a 400km BR.

As an example, the Bryan Chapman 600 (2004 route) is 619km.
BRM you'd get 40 hours.
BR you get 619/14.3 = 43h17m.

The reason for the BRM/BR differences is that BRM rides are required for qualification for the other big foreign rides (Paris-Brest-Paris 1200 mainly). Most of the rides this year are BRM for this reason.

You'll never get less time than the BRM timelimits, so if you keep those in mind then treat any extra time as a bonus.

Below BR you have Brevet Populaire (BP). Which is used for the sub-200km rides where the organiser can set any limit they like. There's a BP version of LEJOG with a 3kph minimum average speed for example, but BP rides don't qualify for points as they aren't completed fast enough to be considered a Randonee. The BR version of LEJOG (with 1400km distance) is 116h40m although the actual figure depends on the controls you nominate.

As for sleep, it all depends on the ride. I've done some with a 10 minute doze on a table: http://lh3.ggpht.com/_91QslVU2iAc/ShJNLQd7MJI/AAAAAAAADhw/jGX0EYDx_8g/IMG_2592.JPG

The Severn Across 400 a couple of years ago I had a 45 minute nap in the cafe upstairs at Membury Services. No sleeping bag required, just find bit of floor and lie down. If I'm tired enough I can sleep on icy gravel. A warm carpet floor is luxury. I sometimes carry a lightweight silk sleeping bag liner (130g or so) but I've never needed to use it.

On LEL I slept at various controls (on the floor mainly) but had an attack of the dozies coming back through Brampton at some stupid time in the morning so I broke out the space blanket and had an hour's sleep in a church porch.

I did the Dun Run as a DIY 400 Audax last year by starting in Dorking, riding to Dunwich and then cycling back home to Putney afterwards. I got to Dunwich at about 6am, had breakfast in the cafe, turned the bike around and cycled back. No sleep at all during that ride.