Roughly a third of the campaign length. A one-week campaign gets ~2 days of teasing; a month-long campaign gets a full week. Teasing builds a warm audience so launch day converts instead of starting cold.
No. Keep the message consistent but adapt the format and caption to each platform’s culture. Copy-pasting the identical post everywhere reads as lazy and gets throttled by algorithms that detect duplicate content.
Pick one primary number tied directly to your goal (sign-ups, sales, leads) and track it daily. Reach and saves are early signals, but the campaign succeeds or fails on that single conversion number.