mine had been on 18-19 years when i went to remove and had the same problem. The rubber mallet is the first way i'd go but if that fails, (mine were frozen) i kept applying my own mix of rust loosening oil -
i use a mix of ATF oil with acetone or mek (maybe 25%) of the solvent to oil. Only reason i like it, a) it's cheaper than the aerosols, and b) i can thin it as much as i want to let it flow into whatever tight fit places
i'd apply as many times as possible, then i used a gear puller - let the claws into that semi-round channel running around the hub, just a bit in from the axle nut - i held the claws into that channel with some 1/8" aircraft cable wrapped thru the spare holes of the claws and pulled em tight, and pinched the ends to one of the claws with vise grips
and used that to pull em off - if they don't come, apply some more oil and let sit for couple hours and do it again. Some items, like the bearings in a blade spindle housing, took me 3-4 days of multiple applications of thinned oil every chance i got
once off, you might want to put a coating of synthetic grease on the axle splines to help prevent them from refreezing to the hubs