I had enough miles for two people to fly round trip in business class from San Francisco to Australia using the United Saver Award (270,000 miles). I did not have enough miles for United Standard Award (600,000 miles).
The United (other airlines have similar products) search engine gives you a highlighted calendar that indicates the days that have saver/standard/business/economy flights. You can scroll forward and backward on the calendar and you can clearly see which dates have business saver dates available. Then scroll down and see the specific flights that are available.
I could see several dates available, but we were leaving for a two week trip to Colorado, so I decided to wait until we got home. BIG MISTAKE. When we got home there were NO business class flights available, and very few economy saver dates. I ended up having to book a date almost two weeks sooner than the date I wanted, in order to book an economy flight with miles. I was able to pay for an upgrade to Economy Plus, which gives you four more inches of leg room.
For the return flight I set an alarm on my calendar to remind me to book as soon as the flights were available. Our last destination in Australia will be in Cairns on the north coast. I could book us on business class from Cairns, but we had at least two plane changes en route. Instead I opted to look at the options if I flew home from Sydney. It turned out that I could book us to fly direct from Sydney to San Francisco in business class with a saver ticket, so I booked that flight.
The lesson is to book early and when you see something that works for you, don’t wait, BOOK IT.
Also, be flexible, about what airports you fly in and out of.