Maintenance hint

I know we all check tire pressures, wheel lug torque, grease bearings, and the normal maintenance items on our RV's, but recently I had an incident that I have never seen in almost 60 years of trailers and towing. I grew up in a shop that built farm trailers and other equipment so I am not new to trailers, but on a recent trip, the main spring bolt of the lead axle on one side of my fifth wheel apparently broke out, letting the leaf spring come apart, and the lead axle slid back, tire contacted the rear axle tire, and the trailer jerked sideways into a bridge abutment. Total cost of repairs over $6,000. Two new axles, two tires and wheels, springs, spring hangers, brakes and wiring, side panel for the trailer, paint,etc. Add the spring bolt to your yearly check list.