The post-1973 Detective Special with the shrouded barrel was factory rated for up to 3,000 rounds of +P ammo.
After that they needed to be returned to Colt for inspection and possible frame replacement.
The aluminum Cobra and Agent were rated for up to 1,000 rounds of +P.
As a discontinued model, I'd recommend shooting standard .38 Special for practice and load the +P for carry use.
The only problem with shooting +P is that the gun will wear faster and need maintenance sooner.
Today there are a number of non+P standard .38 defense loads that are excellent.