Not enough info.
Without a biopsy, they won't know how aggressive it is, but a rise of 28 to 30 in 6 months is a very slow doubling time, which might suggest not very aggressive at all.
What do you think his life expectancy is, ignoring the prostate cancer? On average, it's 5½ years for a male of that age. For a non-aggressive cancer and a life expectancy of 5½ years, he's unlikely to benefit from treating it.
If you think his life expectancy is longer than the average for his age, getting periodic PSA tests would be a good idea.