airline schedules aren't published more than 12 months out (and can change much earlier than that of course) so going via TA won't provide any extra info

But you can make educated guesses. Airlines don't like major changes to profitable routes unless there is a specific need. So if for example your flights are 14 months away, you can get an idea of the schedule by looking 2 months out (ie 1 year earlier). It isnt foolproof, particularly around major events where extra flights may be scheduled, and worth checking (eg by reading/posting on FT) if the route is being dropped or new route starting that may help you. Most of the time it works well.