I think the key is flexibility. Over the past few weeks I was looking for availability to uua from WTP to CW in November. I narrowed it down to Tokyo, Hong Kong, las Vegas and Montreal with availability on the dates I wanted. I booked Montreal.

Most destinations I looked at had some availability, including many in the usa, just not on the dates I wanted. Looking at January (another possibility for me) lots of other options were available.

I can't comment on what it was like in the past as this is the first time I've used avios, but booking early, with flexibility on the destination there are options. I consider the scheme to be working quite well for me.