Let's wait for a little longer time to see the long-term response. It is only 5 weeks. His brain-testicular function will move up and down like a roller coaster in response to the excess sperm blocked trapped the testiscles.
Generally speaking, the brain's testicular negative controller will slow or shut down the testicular function when the excess sperm is accumulated. Once the testicular function is shut down, his body will experience testosterone deficiency, resulting in erectile dysfunction. When the excess sperm is fully absorbed by the body, the negative controller will restart the testiscular function again. Then, his testiscles will produce sperm and testosterone again. Once the sperm is acculumated excessively, the negative controller will slow or shut down the testiscular function again.
You will expect his erection power to be up and down like a roller coaster. His mood will change like that too.
Generally, vasectomy will accelerate the aging of the testicles.