Years ago, there was a pattern of release award space at begin-of-schedule, some 330+ before travel. That is not longer the default situation. There may be some released at that time and a few weeks later but just as common for airlines to wait to see how the flight is selling versus historical data. Then if sales are falling behind, they may release some seats. If sold seats are on historical trends or better, the likelihood of awards space is less. Some airlines are more sophisticated than others and some like UA for their flights tend to hold onto space until closer to departure.

So in summary, predictable patterns are few and award space is getting harder to find.

Business award space for some routes can be nearly impossible to find and generally is never easy. BUT it can happen with some flexibility and perseverance.

A couple of suggestions for finding space
== Avoid peak travel periods -- seasons, days --- midweek tends to be better than weekends, be flexiable -- fixed dates are a killer
== Look early, look late, look all the time
== Partner space tends to be more available than UA space for international flights
== For those not starting at a hub, first look for "gateway" non-stop space to Europe or Asia. Find the long haul flight possibilities first and then build from there (or separate ticket to the gateway -- with plenty of buffer time)

What does "Advance seat assignments are restricted for this flight" mean?

What time (and time zone), how many days out does UA release awards for booking?

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