Laundry-Realize that no mater how often it is done, it is never soon enough. There is going to be an endless pile of shorts, shirts, compression wear, and socks. Doing laundry more often only creates dirty laundry faster. Running attire will be found drying in the shower, hanging outside and sometimes on your side of the bed. A sealable laundry hamper is the best option for combating the smell, but will quickly become overrun by the volume.
Hydration Equipment- Just come to terms knowing that every runner needs water bottles in multiple capacities, soft flask, hydration reservoirs in multiple sizes, and an assortment of gel flask. It is best to designate an area for these to be stored, unless you want a complete take over of all available space in the cabinets. After you get the bottles and flask organized, don't forget to designate a location for the hydration carrying systems. Small handhelds for short runs, large handhelds for longer runs. Small capacity vest for mid distance runs and a larger version for long distance runs. Don't forget about the adventure running pack. I know what you are thinking and no the garage is not a good location for storage!
Alarms- Realize that all though you are deep in a dream with the hottest movie star, you will be yanked back into reality by your runner's alarm. At times as early as 3:30 your runner will be jolted out of bed by the sound of their alarm. You also will enjoy the fun of listening to your them prepare their equipment, stagger into their running attire, and flush the toilet a minimum of three times, before finally heading out the door on a run.
The Other- The earlier you realize that you are the second most important thing in their life the better. Running takes a front seat to anything and everything. The runner views their running less as a hobby and more as a lifestyle. It sounds better as a lifestyle, when attempting to mask one's addiction.
Short Length- The runner will always have a pair of shorts that is shorter then your shortest pair. It is best not to feel awkward about this and to rather embrace the opportunity to admire the strange tan lines they have developed on their gams.
Strava or Bust- If it isn't on Strava, it didn't happen. End of story.
Shoes- Just like hydration equipment your runner demands variety in footwear. Having a specific shoe for every potential terrain is not a desire, but a requirement. Realize that you may have to cut down on your total amount of shoes to accommodate their demand for space.
Diet Fads- Accept the fact that any time a new issue of Runners World comes out your diet will be changing. In the quest for the perfect running physique your runner will try anything. Only fats? No problem. No fats? Of course that makes sense. Only meat? Cave men ran while hunting, right? If diet variety is not your style make sure to have a secret food stash handy at all times.
Eating the House and Home- Know that five minutes after finishing a long run or race your home will be empty of calories. Your runner will devour everything and anything in their line of sight. It is best to keep pets at bay during this time; until the runner's hunger expires.
Vacations- And finally always remember that your runner is always ready for a vacation, to a running specific location or race. All vacations will be planned around their desire to run a race, or epic trail. Keep in mind that even if you don't realize it, your runner is planning a running adventure for that upcoming couples retreat you had planned.