What's so hard? The "He was right!" post said it all. I go about 10 years. $1K or less to protect a $55K or less boat makes good sense to me.
Don't quite follow your post. Do you change your rigging based on sound engineering judgement or a fear factor of the unknown?
For those that say change your rigging every (you choose), 7 or 10 or 15 or 20 or 35 years, do you also change the turnbuckels, pins, chainplates and mast fittings (tangs, bolts, spreaders, spreader mounts) at the same time? If not, why? If you cannot trust a rigging inspection, and you say you will change your rig every 10 years, why in year 9 day 364 is you rig ok, but at day 365 no longer any good?
We trust our lives to about a 1/4 thick piece of rubber for 80,000 miles (tires)with only doing a brief visual inspection, why cannot a rig inspection be trusted?
Just yesterday I picked up a p/u truck load of lifting gear that had just gone through an annual inspection (chain hoist, chokers rated to 9,000 lbs that have swaged eyes, slings, ect.). All that was done is a visual inspection. This equipment like your boat rigging, a failure could kill someone, yet only a visual is done. Also talked with the rigging inspector as to how a 100 ton mobile crane is tested, they do a 125% lift, but then perform only a visual inspection of the cable and fittings- no x-ray.