i agree with all the above; but it is going to depend entirely on your own contribution!
i typically use around 1.5wh per 50 feet climbed on a hard ride, not using the motor at all until the climb is fairly steep. i haven’t done more than 6,000 feet in a ride, but also haven’t used more than half the battery.
the way i’d look at the plan for a ride like this is as follows:
a 6% grade for 31.5 miles is 10,000 feet. it takes 240w for a rider my size to do that climb in around 4 hours (7.5 ish MPH). we know the battery contribution is limited to around 270wh (the motor isn’t 100% efficient and you can’t run it all the way to 0) so you don’t want to be drawing more than 65watts for those 4 hours. (65x4 = 260). that means you need to supply 175 wattts. you are doing 62% of the work (175/240), the bike is doing 38% (65/240). VERY IMPORTANT to note that the creo’s assist setting provides double the percentage listed, so the setting to achieve that amount of assist it 20%, not 40%. if i was riding that far i’d also cap the total assist at 25%, because otherwise if you ride really strong out the gate the bike will also expend more of the battery, and while it’ll be for less time, it’s less efficient to go fast.
long story short, this will be a tough ride without a range extender. don’t use the motor except when climbing, set the assist to something like 20/25, and use mission control to keep an eye on the motor output during your steady climbs.
and definitely let us know how it goes!!