In my experience it really pays to check redemption availability regularly. I've managed to get UC redemptions on the LGW-LAS route 2 weeks prior and that route is notoriously bad due to the very small UC cabin. It can seriously pay to check obsessively, especially if you're travelling fairly short notice. I've often seen seats pop up and dissapear within 24hours as diligent flyers are checking 3 times a day.

I've also had redemptions to LAX, JFK and MIA all in the last few months with no problems.

Having a look now, theres UC availability to NYC almost every single day for many months. Theres tons of availability to Tokyo if you can be flexible and not fly on sat/sun. Theres even some availability for Hong Kong in november, and thats just the first three routes I've checked. Flexibility, as has been said by others many times before, is certainly key.