Back in my day, a confidential was hard to get, much less a secret. My first duty station I only needed a secret because of the intel. I worked with but as soon as I got to the 191st Combat Intelligence Company, 312th MI Bn. of the 1st Cavalry Division they put me in for top secret. Took about 8 months, IIRC.
It was about 3 to 4 months for my TS.