Hey, 40 year olds, get off this thread, dagnabit!
A man's strength peaks in his early 40s. You can't talk about being old until at least 50 or 55.
Technique is everything. You can't blame age unless you were already a 500 foot thrower and can't do it anymore.
Proper technique gives more distance, and less wear and tear. 50 year olds are still plenty strong, they are just more likely to get injured.
One big thing I've learned in the injury department: do not wear shoes with really great traction, as that prevents spinning on your heel properly in the grass on fairway drives. That causes really bad stuff to happen in the knees and back.