Can I close my Amex platinum and gold, and then reapply for the same cards again a month or 2 later, and then churn those miles again for 75k and 100k miles?
YMMV, however, this can trigger a FR. If you are not earning the salary you claim on the application, then be careful.
You can also be denied due to "abuse of rewards program".
Search the forums here for more details.