I do this as well. My system is that the end slots on 2L or 3L pins are horizontal if the pin is parallel to the ground plane, and lined up with the main longitudinal axis if the pin is vertical. Typically this means the end slots are aligned with the beam they’re going into (though not always!). The bush slots then line up with the internal slots of 2L/3L pins (i.e. generally top/bottom). I sometimes make an exception to bushes where they line up with other bush’d components (e.g. 2L perpendicular connector with axle hole/pin hole) on a common axle. It is annoying sometimes when a subassembly is assembled in some different orientation :)

I don’t do it because of any OCD tendencies (at least I don’t think so!) rather as it just slows the build down a bit, and I enjoy it a bit slower :)

I don’t do pins but I do bushes. The slots have to be in line and the knurled ends have to join to something else knurled like a connector if one is next to the bush, or if two bushes are next to each other then I’ll have the knurled ends facing each other.

Also, it’s not OCD, it’s CDO.

I only do it with bushings and [+o] pins. Especially why they have to hold something more heavy or have pressure on them.

Not in the slightest tiny bit. Some of us need more important things to worry about!

I remember years ago a thread about something to the tune of "what are you OCD" (in regards to building) about?  I'm not going to take the time to look it up, but I remember pin and bushings orientation being discussed. 

I personally don't care, but I do know that it has made a difference in my building in the past.  I can't remember an exact example, but inserting a bar or something in a pin already used has made a difference in the past. 

But I do remember a specific example of when the orientation (or direction) of a 3L blue pin mattered.  As others have already pointed out, the direction makes a difference in disassembling a model and making things accessible.  But a few years ago when I built a Technic Version of the U-wing: 

I had a terrible time with the wings drooping when in their forward position.  They did not droop because the Lego used was not stiff enough, they drooped because their starting point (where they attached to the fuselage) started in a downward position.  But by orienting the blue pins like this: 

(wing direction going left to right) I was able to fix the problem.   As one can see the addition "ridge" (i.e. additional ABS) was just enough to lift on the right and push down on the left.  Fixed my problem perfectly!

Edited September 14, 20213 yr by nerdsforprez

I just never had the idea of checking this on my side... Since I started my Technic life early with 80's sets when only frictionless pins existed, it never came to my mind.

However, when using 3L pins, I always try to follow the instructions' way to insert them inserted, I mean which way to put the physical frontier between the 1L and the 2L side : am I the only one?

Edited September 16, 20213 yr by Celeri

The OCD is real! I always am conscient to the pin and slot directions when I build, and even mildly annoyed at how often the instructions of official sets have them randomly placed... 

_ED_