When your CB whip hits the stoplights in town (It's pretty close in my choptop, it usually dings on low underpasses an stuff, the tip is around 13' 8" off the pavement...)
When you go into the parts store for something and when the pimply faced kid behind the counter asks what year make and model you have, you just laugh. (I've had to tell the hard-headed ones more details and usually they fold quickly cuz they don't know what to punch in... Well it's an 89 2wd with axles from an 86 4x4, explorer leafs, etc)
When you can sit under it comfortably to replace the starter.
When your floor jack no longer is tall enough to lift the axle.
An ammo can makes a perfect seat for working on the brakes or polishing the rims because they're that far off the ground.
6-ton jackstands don't reach the frame when the truck is on the ground.
You park it in a parking lot and come out of the store to find "hardcore" jeep guys looking your truck over. (True story, guy parked his TJ next to my choptop, he was on 33s and impressed with my blue camo monster)
Your significant other has insisted you put some sort of step on the truck so it's easier for them to get in. (and possibly your response has been... let me fire up the welder, I think I got an extra piece of chain in the back of the garage that'd work, I don't want to limit my clearance)
Your friend looked at you when you got done lifting it the last time and said "I'm not riding with you in that!"
You have to stand on a bumper or tire to check your oil.
You plan your custom front bumper with that in mind...
You consider making a custom spare tire carrier for your Bronco II because you can no longer reach the lever to release it without a ladder.
I got a ton more but I'm already late for work, lol