I agree with natas; what I have always read was the any changes should happen slowly, a couple degrees over 24 hours shouldn't be a problem but I would caution about the fish you keep, especially if the high side of your curve is near 85. There are many fish and critters in in the hobby that would not tolerate the high temperature and with higher temperatures come the need for higher aeration so that sufficient O2 is available for the tank inhabitants.