You don't say what happens when the coil dies, is it burnt hits, loss of flavor, etc... Knowing what you experience will help us guide you in the right direction. Reply with more information when you can.
Priming the coil properly and breaking it in slowly is essential to longevity and flavor. I assume since you only go through 5 ml per day you don't chain vape and burn the coil out prematurely.
Just because a coil is rated at 60 to 90 watts doesn't mean you need to hit it at 60. I get a nice vape on the Mesh Pro double at 53 watts. I start the double around 28 watts when I'm breaking it in and work up in 3 to 5 watt increments until I hit the sweet spot for me. Each person and juice will be a bit different. Different juices can have different sweet spots when vaped with the same tank same coil. Its best to slowly work up with each and note the sweet spot for each juice in each tank coil combination. My NRG tanks tends to run 10 watts below my Freemax Mesh Pro for the same juice.
Watch this video and see if it gives you any new ideas on priming and breaking in.