You know you are an Audiophile when:

Because you are into analogue, you buy a cassette deck, then you buy another cassette deck, then you buy a reel to reel tape deck, then.........

You do it in the dark.
You do it by yourself.
You yawn to pop your ears before your activity.
You don’t want to be prematurely interrupted.
You moan quietly “oh, that’s the spot...”
You mumble to yourself “I know I put it somewhere.”
You need more power than a theme park.
You get taken for a ride every time.
You must leave your significant other to engage in what you love best.
You use the needle to get high.
You are engaged in high fidelity and yet you claim your in-laws are into infidelity.

When some of your internet passwords are the make and model of some of your most revered audio components...

Hahaha... @highfi - "You do it in the dark./ You do it by yourself." -- this cracked me up. Absolutely. 

You have a dedicated audio room. Absolutely, with audio engineered construction at $500/sq ft.

Your listening chair is in the “Sweet Spot”.  Not really, three sweet seated sweet spots.  I dislike head in a vise sound.  Maybe four sweet spots.

You have sound treatment on your walls.  Radical inside the wall treatment and substantial side wall and suspended ceiling treatment.

You spend hours properly placing and tweaking your speakers.  I did spend about an hour placing speakers but four hours tweaking the SR HFTs and four Hallographs

You understand that properly placed speakers will create a 3D sound stage (placing musicians and singers in localized positions… from  left to right… front to back) [Sound-stage]  Absolutely

Your stereo is worth more than your vehicle.  Absolutely

You know that higher end components do a better job of: being less fatiguing to listen to, creating the imaging (sound-stage), representing the instruments more accurately and with more detail, are more involving.  Higher end but not necessarily higher cost.  

You are intimately aware of the performance and tonal quality of your system, and can describe the results of any changes in the system.  Absolutely.

You are aware of how bad the sound is for the first 3 - 4 songs at any live music event.  Not necessarily.  I am a part time recording engineer and the orchestra, chamber group and choirs I record make sure the sound is set from the start.  I have 100s of my recordings to prove that.

98 % of the time… when someone cranks their stereo up and says “This sounds GREAT” you cringe. You could list all the ways and reasons why it sounds awful… but you don’t.  About 80% of the time.  I'm not entirely happy with several friends high end systems but they are enjoyable to listen to.

When listening to music… you spend a portion of time listening to and exploring the placement of the sounds in the sound stage, and the quality and detail of your system… with your eyes closed.  With the lights nearly off-as in a concert hall or opera.

You become aware of how bad the sound is on some recordings.  Only poor mastering is generally the cause.  I listen to the music with the sound quality that I expect from the recording/mastering engineer.  I listen to 10,000s of 78s every year as well.

You are painfully aware how awful sound systems are at bars and clubs. Absolutely

You have increased the sound performance of your system through upgrades and tweaks... multiple times.  Upgrades mostly 15 years ago, many tweaks last five years.

You are aware of sound reflections in your home, and live music events.  Yes

You continue to learn and try new things.  Absolutely

Out of curiosity… you try various things on your system… to see what, and if… there are any improvements… ie: cables, cords, isolation, dampening… etc.  I am a beta cable tester for a manufacturer who has had me test about 200 cables in 20+ years.  He has settled on final designs in the past two years.  $400-$1000 ICs, A/C and speaker cable for Masterbuilt quality sound.

I am an audiophile second, music lover first.