Armyman2069

@Armyman2069 because you are 90%, please check my blog entry. It talks about the various rating protections over time (5, 10, and 20 years). It goes hand in hand with what @broncovet noted about 38 CFR 3.344. Additionally, if your physician states your disability "is not likely to improve" the VA is more likely to consider it stabilized.
 

I agree. 
This vet was awarded for  costochondritis as secondary to his SC respiratory disability:
"Additionally, during an August 2013 VA examination, the examiner specifically stated that costochondritis was a condition of the musculoskeletal chest wall, not the lungs and that it was neither caused nor aggravated by the Veteran's respiratory condition but could possibly be caused by coughing.  As the Veteran's coughing is shown to be due to his service-connected respiratory disability; as the July 2008 medical examiner specifically found that the coughing was in turn causing the costochondritis; and as the August 2013 VA examiner indicated that the costochondritis was musculoskeletal in nature, the evidence reasonably shows that the Veteran's costochondritis represents a separate musculoskeletal disability resulting from his underlying service-connected respiratory disability.  Accordingly, service connection for costochondritis on a secondary basis is warranted.  38 C.F.R. § 3.303, 3.310.  The nature and extent of this problem is not before the Board at this time."  
 
ORDER
 
Service connection for costochondritis is granted.  
https://www.va.gov/vetapp15/Files5/1541975.txt
This vet apparently had a SC “0” % for his costochrondritis ,but BVA awarded him 10 % for the” entire rating period  of the appeal.
The decision contains Diagnostic code info.
https://www.va.gov/vetapp19/files9/19172161.txt
This also is a grant for this disability:
https://www.va.gov/vetapp19/files7/19155472.txt
This another grant because BVA found this disability to be secondary to an established SC.
In summary, and after resolving any reasonable doubt in the Veteran’s favor, the criteria for an initial 20 percent rating for costochondritis associated with a residual scar, status post right lower lobe segmentectomy, have been met throughout the appeal period.  See also 38 C.F.R. § 3.102 (2018).
https://www.va.gov/vetapp19/files7/19153370.txt
You said:
"Also, I was denied a claim for chest pains when I got out, however, years later I found that I was diagnose with costochondritis while in the service and twice since I have retired. Should I reopen my chest pain claim or just file a new claim with just the costochondritis?"
If the denial was generic- just for chest pains- I would file to reopen that claim with the proper diagnosis of this condition, with the proof from your SMRs ,that show you were diagnosed in service, and with any other proof that it is a chronic conditions well as if it is secondary to anything you have now that is already SC.
On the older denial, does it show that the VA reviewed your SMRs?
 
 
 

Good advice already given.  File an intent to file and that saves your file date while you are getting everything together.  If you are denied the first time go around, do not give up like they want you to.  An ugly secret of the VA is that a lot of valid claims are denied first time out.  The BVA overturns many denials.