Having multiple tanks is great, but having multiple tanks that use the same coil is better.
I use 10 tanks in rotation, 6 subtank minis/toptank minis, and 4 subtank nanos, they can all use the same coil.
Whatever your choice in tanks are Crown tanks, or Smok, or eleaf, its a good thing to try to get tanks that all use the same coil, it just makes things easier.