Like Bunnykiller replied, it all depends on the NET.
I have some that require changing my wicks in less than 2 mls, so that means twice a day. I have others that allow up to 3mls so once a day is needed. I have some that are cleaner and I can do up to 5ml so that means every other day.
I have different atomizers for different NET use. I have a couple RDAs for the real disgustingly dirty but most tasty ones. I have some RDTAs for the less gross and a couple RTAs for the cleaner ones. That keeps me busy in the upkeep and I have to daily dry burn at least 2 RDAs and up to 4
tanks. Its the price I pay for my love of NET.
For my light fruity liquids I can go through 20mls with the same wick. Im a heavy vaper and go through 20 to 30 mls daily. My NET use is not all day but still costly so I ventured into DIY NET. I still buy a few from Naturally Extracted Tobaccos , so good and gross and costly with my heavy use.