Are you sure it is rubber? If it is truly rubber and has cracks, then it needs to be replaced or repaired. Any roof that has cracks cannot be magicly healed by a coating. If a surface coating has cracks that do not extend into the structural membrane of the roof, then it should be recoated to keep it intact. That is normal maintenance. If it is rubber, don't let anybody near it with any kind of asphalt, hot or cold. What is on the surface now?
I think Maintenance 6 is referring to rubber as in EPDM, if that is the type of roof your talking about than any type of asphalt repair should be avoided.
If it's a rubber roof as in a torche down product than an asphalt solution would be ok.
Like Maintenance 6 said tho, you have to make sure your roofer is going to repair any damaged area's with roof cement and membrane, or other materials to patch any bad seams or cracks in the field and flashing materials before they coat it with anything.
You can easily get numerous years of added life out of your existing roof using wither of your two posted methods as long is it's done properly.
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