Amex SUB Offer - How long does it take ?

Hi all, I got a sign up offer for Amex Platinum for 175k points if you spend $12k in the first 6 months. I am half way there and 4 more months to go.

My question is, how long does it take for you to get the points once you meet the spend? Is it immediately or after the offer expires in 6 months? I’m close to meeting it and want to use points to book an airfare in the fall, so not sure if I should purchase something I’ve been eyeing to meet it sooner than later, or book my airfare now and wait until I accumulate the points for future travel plans. I wouldn’t want to wait too long and miss out on a good deal for fall travel.

Thanks all!