do new AC flights periodically get released for award purchase?
 

I'm looking at booking a flight in February 2020 using my Aeroplan reward miles. YEG -> NYC -> MIA -> YEG. For the first two legs, the available flights aren't all that good--long layover and early-morning departure. If I were to wait a month or two, is there any chance additional reward flights might become available? Does that occasionally happen with Aeroplan? If the answer is "no", then I'll go ahead and book the flights now.

The answer is "maybe". In a few hours or days more space could open up. Or not. If it does open up, and you've already booked, you might be able to change with a tolerable change fee. Or not.

If the options today are tolerable: book it.

Oh, OK, thanks...wasn't sure if they basically "locked in" award flights once they are announced, and that's it.

The itinerary right now actually looks doable now that I look at it again...the one thing that's killing me is that the return flight from MIA to YEG includes a 3-hour flight on rouge with its 29" pitch seats (I'm 6' 4"). I'm tempted to just book that flight separately on expedia or something :) And unfortunately all the other possible departure points in the area (FLL, PBI) all use the same rouge flights out :(

Try calling in to make the reservation and see if they can ticket you in J for that leg. May not be many points to do so.

There are mixed cabin bookings all the time, but I realize that puts the reservation into Business. My point is that sometimes the redemption cost is reasonable.

In this instance, if I did an open-jaw in economy that looked like this:

Option 1
Feb 3 - YEG - EWR
Feb 10 - EWR - MIA
Feb 17 - MIA - YEG

In Y, it would cost me 50,000 miles + $185.33.

If I did 2 separate bookings that looked like this:

Option 2
Booking 1
Feb 3 - YEG - EWR
Feb 17 - MIA - YEG
In J, it would cost me 67,250 miles + $114.87

Booking 2
Feb 10 - EWR - MIA (MIA-YYZ-YEG)
In Y, it would cost me 12,500 miles + $7.40

For an Option 2 total of 79,750 miles + $122.27. 29,250 miles more and $63.06 less than the first routing, with the return legs MIA-YYZ-YEG all in J.

All I was saying is that agents are sometimes helpful in being creative here, and it may not cost that many miles to do so.

It appears you're quoting the Priority Reward pricing at 50K for that itinerary. OP does not appear to have any status and is therefore likely looking at X space for 25K miles. If this is an X redemption, there's really no way to add J on any portion of it without a very high cost.

If you're using an inflated Y price (either Y IKK or Market Fare) as the baseline for comparison, it might start to make sense, but I would doubt that's applicable to the OP's case.