The documentation for this endpoint states that
"The API prohibits batch sizes of larger than 1000 for scheduled pushes, and batches of larger than 100 for push to local time scheduled pushes."
Does this mean we can only have 1000 scheduled pushes at any given time? Or that we can send a batch request for upto 1000 at a time ? If so, is there a total limit on how many pushes can be scheduled in advance?
This means that you can send a batch request for up to 1000 at a time.
There are no limits to the number of pushes that can be scheduled in advance, however, do note that each scheduled push will have it's own Push ID that you'll need to keep track of in case you ever need to edit/delete that push at some point in the future. With this in mind, you'll want to make sure that the number of pushes you schedule in advance is something that you can easily manage/track (10,000 scheduled pushes might be a bit much to track at any one time, but it depends on your infrastructure).