Any temperature over 140 will void warranties, 125 for some. Hot water baths expose the ball to temperatures too high for too long, they also don't extract the oil, they just get out whatever happens to bleed out. This still leaves trapped oil in the shell near the surface, which is why even though oil may come out, it may not improve the ball reaction much, if at all, and it will certainly take forever. Storm and Ebonite brands soak up the most oil, and the First Blood has had loads of problems "dying" around here.
Put in a request with your local shop to purchase a Detox, 30 minutes and you essentially have a brand new ball, all done safely, quickly, and without voiding any warranties. Revivors and Rejuvenators are now obsolete.