How long after taking my final C&P will I get a decision?

Finished my last C&P in November. Final decision in April. It really depends on total years of service, length of medical records, and total number of claims. I retired at 17.5. As your PEBLO will tell you there is no real concrete timeline. It sucks but it's really just a game of wait and see.

I think it all depends on the individual. I'm in a couple of groups on Facebook because I see ranges from immediate to years. My person timeline was fairly quick:
October 2019: saw VSO
November 2019: got paperwork stating timeframe (appointments)
December 2019: C&P
January 2020: decision made
December 2020: 1st payment

Just make sure that when you have your C&P before getting out (same advice if you're already out) that you tell them everything that's bothering you, no matter how small it may seem to you. Even if you come out with 0% ratings, that's still a rating (so long as it's service connected) and you can always go to have it changed. That's what I did. Took me 3 years to go back but when I did finally see a VSO, my rating increased tremendously.

Let me add that because I took the separation pay, I have to pretty much pay that back before I can receive my compensation. Luckily for me, it wasn't "too" much so I only have to wait 10 months since they backdate it to October 2019 and I didn't know I had gotten a rating until February (because I wasn't checking ebenefits). Please note if you took/take separation pay, it has to be recouped.

The VA will say they have a year from your date of claim. With that being said, it really depends on a number of items, 1. The actual claim and the supporting documents, Medical opinions, buddy statements supporting the injury or illness. Military records showing the incident or other forms of documents corroborating the incident. If those items are in place when the C&P is completed there is a good chance 3 to 6 months a decision. As a CVSO I have seen it vary from one month to a year.