I switched to steel cans only a while back. The ones I have are Justrite brand. I keep them in the attached garage along with two mowers, an edger, a tractor, a snowblower, an ATV, a power washer, two cars and a pickup truck. If all the vehicles, cans and equipment are full I'd have about 95 gallons of the stuff. I don't take it lightly but how far do we go? I buy good cans and keep them on a chunk of rubber mat to avoid corrosion, and I keep the equipment in good condition. The cans sit next to the extra propane tanks under the cabinet with 10 gallons of motor oil and various solvents. Fortunately I don't have a Tesla or I'd have to build a shed for it.
I take reasonable precautions but never felt I need a separate building for my gas cans.