A decent coat of wax, glaze, sealant--whatever you use every couple months and the rustoleum lasts pretty well.
I had a 79 cherokee cheif 4 years ago that got the rustoleum treatment--took over 2 weeks to cure (and that was in Florida in October), other than that it looked great.
Cant be beat for $40 in materials with a little more upkeep, and it definitely beats the color match bombs at the supply shops--hell they want $25 a can up here! Some Napa's do it for roughly $15, but my local one doesn't.
here's a pic of my 79'. Its the result of 3 days of clueless back yard bodywork and sanding, some rustoleum, and herculiner after peeling the original flaking chrome bumpers with a chisel and a pair of plyers! I scraped the flaking chrome off the grille with a razor blade, sanded it down and shot it with metallic silver. Sure looked good after.