I weigh between 80 and 85kg.
Have never broken a spring or a Brooks rail, but I am aware that others have. I think Dan has.
Before I decided which to take, a B17 or a Conquest, I would decide which one is more comfortable. The B17 is a bit wider and flatter in back. Both have parts that can break, but the shape is different and I think the feel on long days in the saddle is a more important factor to consider than the potential of a broken part.
If I was going to ride more of an upright position, I find a B17 feels pretty good. The Conquest and Brooks Pro have a nearly identical shape. I find that when I use the drops on drop bars, the B17 (or its sprung equivalent, the Flyer) does not feel right for me, for using the drops I prefer the shape of a Pro or Conquest.
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I recently put a Redshift suspension seatpost on my light touring bike. That bike has tires that are 37mm wide, so it can transmit the bumps to my hands and bum more than bikes with wider tires. The Conquest has rails that are far from horizontal, the seatpost did not have enough range of seat angle to use the Conquest, so I put a Pro on that bike. So far I have only about 25 miles (~40 km) of riding with it, but so far I like that suspension seatpost. Their instructions gave a setting by weight for "comfort" or "performance" I set mine up for performance and am quite happy with that setting.
https://bikepacking.at/media/pdf/a2/29/0b/Instructions-ShockStop-Seatpost-Rev-1.pdfThe Redshift is not cheap. I got a 25 percent discount on a limited time sale.
If you consider a suspension seatpost, Dan has much more experience than I do.