I had seen the LHR loads which made me think that it would be as close to a sure thing as one can get.

We have one way award tickets over and back and sure to business constraints (I have to work until the day before) and that we're going over with friends, we'll use them and not try to nonrev. The return I is a different story, very high fees and taxes (VIE-SVO-JFK) and a long flight, even in J.
We'd also like to visit friends in AMS so I guess we'll go there unless our looks like we can't get out nonrev. We have until 72 hours before the award flight to cancel and get a free redeposit of miles and$. If we do that and don't get out of AND in 2 days, we'll go to LHR.

it'll still be cheaper than the award tix.