Primary Requirements - Long Battery Life and Long lasting durable phone. Note 8 seems enticing but the new S9 rumours that surfaced this week seems pretty amazing
If you need a phone now, no sense in waiting another 4 plus months.
S8+ gets a little better battery life than the Note 8, same internal hardware. That's if battery life is the most important thing for you.
Personally I would get a Note 8, as I like the dual camera set up currently unique to it and the S Pen. Even if the S9 was available today I would take the Note 8 for the pen, but that's me.
You're right about the rumors. And the Note 9 is supposed to be even better (which is why I'm waiting until next year). But "long battery life" (if you're talking about the time between charges, not the time between replacing the battery) and "Android" don't go together. That's one place where iPhones have it over Androids - longer battery life. Samsung tried - with the Note 7. And only proved that you can't have a cheap high capacity battery and a small (relatively) phone in the same package. Lithium batteries give off heat, and if the phone is too small for the heat to be removed, the phone starts acting like a weapon.
One solution is a power pack. With an almost indestructable 7500mAh power pack available for $20, that's one way to get battery life and Android.