Well, I've always overdone the maintenance on my cars on the theory that, maintenance items like fluids and filters are cheaper than parts and components and an over-maintained car inspires more confidence on a dark and stormy night than a car maintained to even the manufacturer's minimum recommendations.
Also, I like getting all of the maintenance taken care of once in the Spring and once in the Autumn. That leaves the hot summer and holiday rush of winter free of car maintenance concerns.
My little brother is 28 and he has a badge. I suspect that, although he isn't towing anything or doing much mountain or off-road driving, his car gets a good workout regularly.
30,000 miles in a year is pretty crazy and I don't expect that the rate will be slowing anythime soon (although he is getting married this year and that tends to slow down the best of us).
I pegged the differentials as something that should get attention. It snows a fair amount in New York and I am sure that he gets a fair amount of wheel spin. Do those cars have limited slip or open differentials? Does he need an additive for the limited slip? Is the lubricant reservoir for the front differential separate from the one for the transmission?
I may be old school but, I believe two coolant changes a year is good practice. Change it once in the spring with a summer mix and once in the autumn for the winter.
At the rate he's going, by the time he gets to September, he will have another 15,000 miles so I am going to recommend that he does all of this stuff now. As for the transmission, its up to him but a few dollars worth of gear oil is cheaper than a transmission and it will inspire confidence.
He already bought the Chiltons.