You can never have too much insulation. Plus it pays for itself. I doubled all of insulation in my attic from R18 to R36 and silicone sealed all cracks. My all electric monthly bills dropped from over $300/mo to around $130/mo in Jan and Feb. Huge difference in comfort and the heater never kicks on until it gets to 36 degrees outside. Much cooler in summer as well.
I still have some homeowners labor left in me ... won't pay for someone else to blow an attic.