When You buy a house just so You can grow Your own killer buds.
When Your using Your grow lights to exclusivly heat Your house during the winter time, and you practically live in FREEZING Canada.
Recirculating the air from Your grow room, through a carbon filter to Your kitchen.
When all Your windows in your house are all fogged up and dripping with water because of the latter ^^^
When You can't have anyone in Your house past 8 o'clock because the 900 cfm inline fan starts up and sounds like a small jet engine in Your kitchen (thats where I ran the duct to, it was the closest room).
When I (You) can grow the best weed that I ,and My friends, have ever smoked.
When You know practically know everything there is to know about growing Herb.
When You have to set up a subpanel to power Your grow room.
When Your buying 3 gallons of super concentracted nutes at a time.
When You marry a girl because her name is Mary Jane
(This doesn't apply to Me though)
Thats got to be up there. Top 10 at least.