Just going by the math, the break even point against an 8% investment return is a lifespan of around 78, or pretty close to average. If he has a good shot at living past 78, cashing it in and investing it and the premiums (with a moderate/aggressive strategy) would most likely result in a greater return. If he has risk factors such as smoking, drinking, stress, diabeties, or is overweight, it may make sense to hang on to it. How old are his parents, how is their health?
Given how close to average the return is, it would also be helpful to ask if he would feel more secure with the $36k in the 'stache and $1000 less in annual expenses? Or would he feel better about leaving an estate to you, your children, and possibly grandchildren.
If you decide to keep it, it might be worth reshopping the policy. Given the longer life expectancies now vs 48 years ago, the premiums might be lower for the same policy.