Does the checkride, by way of a regulation or rule, have to be taken within an x number of days from the day the written exam is taken?

I believe you have 2 years after the written...

Makes sense. Thanks.

I am sort of in the same area for questioning this as well. I will take go through the ATP-CTP course so that I can take my written ATM exam, but I already have a type rating from the military aircraft I fly. Do I still need another check ride after the course and test in a different aircraft to get the ATP or can I use my annual?

I believe you have to take the test, I'd have to look at the 8900 section to be sure, but I remember the highest certification the FAA will "give" to Military is to the commercial level, the ATP level requires test.

Also, ATP writtens are good for 5 years, vs. lower certificates where it's only good for 2.

You will have to take a FAA ATP checkride.

Say you are an E-4 driver. Under 61.73 the FAA will issue you a commercial MEL with an instrument rating and a B-747 type rating. When you complete the CTP, pass the ATM written and pass an ATP checkride in any multiengine aircraft you will get an ATP MEL with the B-747 type rating at the ATP level.