I second what Sam said – comfortable, not fragile, not ruined by a soaking. My Professional's still in excellent shape after 25 years with me (Jesus, saying that makes me feel old!), and the Brooks B17 on my Dad's old Claud Butler (from the 1950s…) is also still going strong, unlike my Dad – kit that outlives its owner.
I proof mine – only very occasionally, like once every couple of years (ahem) – with something Mrs F uses on the leather things she steers her horse with, rather the Brooks proofide stuff, and for the last few years it's lived on my mudguardless used all year round SS MTB (until I got an Ortlieb Mudracer saddle bag – the rails on the Brooks are too wide for the Ortlieb's mounting bracket, and I haven't got round to making a new bracket – when I do, the Brooks comes off the road fixie and back onto the InBred).