Yeah, I've done a few
1,000-1,600+ mile days . . .
There's some great advice here (keep hydrated, eat light, stay alert), some average advice (Airhawks and sheepskins work for some folks, but a true custom saddle fitted to you is so much better), and some really bad advice, too.
Stay away from any powders, creams, or anything like that. You still sweat, but all that happens is that it gets absorbed by this stuff, then you end up sitting in a slimy paste of their chemicals and your own sweat. That's not what you need to stay dry and comfortable for days on end.
Get the right breathable under gear and forget the cheap powders. Your butt will thank you.
If you're experiencing posterior discomfort after long days on the road, you really should look at your riding gear. That can have a huge impact on your overall comfort level as the miles and hours pile on.
Make sure that your riding pants have no seams anywhere near where you sit. It's a small thing, but can make a huge difference in comfort over the long haul. And it's a concept than many manufacturers either don't understand, or they ignore so as to get more product out of a fixed piece of material (saving them money while selling you an inferior product).
Personally, I like the Aerostitch AD1 Pants
, which are waterproof, breathable, comfortable, and have no seams to sit on.
And under that goes LD Comfort
No denim. No cotton. And no cotton/poly blends. All that stuff does is retain moisture and cause irritation.
Quite simply, the material LD Comfort uses is superior to anything else out there. I stay dry and comfortable from freezing temps to well over 100 degrees. It just plain works.
I have a couple pairs of Under Armor gear, as well as some off-brand stuff. They sit at home on the shelf, mostly due to the fact that they're always slipping down and the fact that they don't work well over a very wide temperature range. They're just not comfortable for the long haul, so they stay home. Cheaper doesn't matter if the product doesn't work.
My AD1 pants and LD Comfort gear is all I wear for long rides (and most short rides, too). I have lived in them for weeks at a time while on the road, including a 2-week, 15,000 mile ride.
That's what works for me.