Some growers treat their cannabis plants as a source of joy even before they produce marijuana. Not everyone, though, can take the pleasure of looking after their plantation every day as a hobby. For reasons of security or lack of time, many people choose to limit their visits to the spot to the absolute minimum.
The unique climate required by cannabis plants has to be maintained anyway - fortunately for those that cannot control it on their own, there is an array of devices that will take care of your plants while you're away.
The temperature, humidity, CO2 levels, air ionisation etc all need to be kept at particular levels - neither too high nor too low, as it will affect the final crop of marijuana. Climate control tools allow you to programme the desired levels in advance - temperature between 24 and 28 Celsius (75-83 Fahrenheit), humidity 60-80% (and 40-50% during the last 2-4 weeks of flowering) and CO2 at least at the natural concentration of 340 ppm (parts per million).
Simple humidifier or heater will do only if you can turn it on and off manually whenever it is required. For more advanced setups, you may want the sensors and processors to do the job for you.