IMO If your chassis not rusty then it's worth doing if you drive your van daily.
I did mine and found it to be an easy and very satisfactory job once completed.
Whiped the Wheels of and jet washed all the arches and suspension components plus chassis.
The pressure washer uncovered a large rust hole in one of the arches which I wasn't aware of, I got that welded up.
Then I bought cans of dinitrol 4941 (an amazing product) and sprayed under the arches and suspension components, and applied waxoyl by brush on the chassis.
Also pumped dinitrol 3125 in the sills, doors and chassis rails. Still got more cavity waxing to do once the weather warms up.
I'm pretty confident that I can say if I handnt protected my inner arches id be looking at more arch welding .
