Ok I admit, I didn't know what a g50 atty was. So it's a bottom coil clearomizer - like this one?
If so you can (and should) rinse it out after every 2-4 fills. If you are using a darker, thicker
juice then go with every couple of tanks, if it's a thinner, lighter
juice, then every 3 or 4 should be fine. All you have to do is unscrew the tank from the bottom and run it under hot water. Give it a good rinse and then shake and pat it dry. Clean the inside of the tube with a q-tip if you like - won't hurt.
If you do this, a head will last you a few days to a few weeks (it's really hard to say)
You'll know it's time to replace the head as you will be getting less vapor and less flavor.
At that point, you can try a good rinse and a dry burn to remove all the gunk on the coil. If you want to do a dry burn just rinse and dry the bottom section of the clearomizer and then put it back on your battery - without the tank on top. Pulse the fire button on your battery while gently blowing down the tube on top of the head.
Repeat this, pulsing the button on your battery for 3-5 seconds several times until you don't see any white smoke coming from the coil and you should be able to see the coil glowing red when you look down the tube.
Give it a final rinse (this is important as it will rinse away any gunk you burned off, you don't want to vape this) and dry and reassemble. Doing this might give you a few more days out of a dying head / coil.
Don't forget to buy replacement heads before you need them!