Should you play for 5 hours and let the xbox slim 4gb modded one breaks 6 hours and play again for another 5 hours

Instead you should just put more fans inside by wiring in parallel (not too many or you will blow the fan header circuit) , for the time being just place a pedestal fan in the intake vents (feel if its cool/hot = intake/exhaust) of your xbox and take it out of the shelves/entertainment unit , since the rrod is caused by the /gpucpu contacts (solder ball) expanding and cooling eventually thinning out the contacts and cracking them