[AmandaK]

I don't understand the need to keep them pressurized just to have to depressurize prior to filling with beer.

Couple of reasons.  Pressurized means nothing is getting in there.  It will remain sanitary.  Also, since I'm sealing the keg while wet with Star San I want to avoid oxygen.

That's right, plus I have some kegs that leak a little and I can check to see if it held pressure since the last use.

All of our kegs are old used ones. Many of them are finicky. I have to make sure they hold pressure before I put brand new beer in there. They all get a little blue tape tag that says "S + P" for "sanitized and pressurized".

[HoosierBrew]

I don't understand the need to keep them pressurized just to have to depressurize prior to filling with beer.

Couple of reasons.  Pressurized means nothing is getting in there.  It will remain sanitary.  Also, since I'm sealing the keg while wet with Star San I want to avoid oxygen.   

+1.  I like knowing before filling with beer that the keg still holds pressure, too.

[brewsumore]

I clean/sanitize/dry my kegs, and then store dry with the lid on (with painter tape labeled "clean/sanitized"), and quickly re-sanitize and drip dry before filling.  I normally add keg lube to post o-rings when still wet with sanitizer prior to drying/storing them, but wait to lube the lid o-ring until immediately prior to filling the keg with beer.  I don't feel the need to purge corny kegs of o2 prior to filling them (from the bottom with an auto-siphon), but immediately purge and then pressurize kegs as soon as filled.

[beersk]

I don't understand the need to keep them pressurized just to have to depressurize prior to filling with beer.

Couple of reasons.  Pressurized means nothing is getting in there.  It will remain sanitary.  Also, since I'm sealing the keg while wet with Star San I want to avoid oxygen.   

+1.  I like knowing before filling with beer that the keg still holds pressure, too.

Doesn't mean it will be holding pressure just fine that when you pop the lid, fill it, and close it up again...
Since I do a closed transfer from keg fermenter to serving keg, I don't have to worry much about that. Just make sure it's still holding pressure from when I cleaned and sanitized it.
My keg fermenters I usually clean, and leave the lid sitting halfway in the keg and let it dry out. Then I'll rinse it out and run starsan through it on brewday. Regular kegs get cleaned, sanitized, and pressurized until I'm ready to put beer in them.

[HoosierBrew]

Doesn't mean it will be holding pressure just fine that when you pop the lid, fill it, and close it up again...

No, it's no guarantee but it's a good indication for me. I always leak check with a starsan spray bottle regardless. Don't like bad surprises.

[beersk]

Doesn't mean it will be holding pressure just fine that when you pop the lid, fill it, and close it up again...

No, it's no guarantee but it's a good indication for me. I always leak check with a starsan spray bottle regardless. Don't like bad surprises.

Same here. Sometimes I wonder if it doesn't detect the slowest of leaks though; the kind that won't drain your co2 tank, but will make the beer take twice as long to carbonate.

[Iliff Ave]

I only have 1 spare keg to my 4 on tap. When I kill a keg, I pull it out of the fridge and let it sit under pressure until I am ready to refill it. I will clean and sanitize right before filling.

[Joe Sr.]

I only have 1 spare keg to my 4 on tap. When I kill a keg, I pull it out of the fridge and let it sit under pressure until I am ready to refill it. I will clean and sanitize right before filling.

That's pretty much how I do it. Then I clean a few at a time.  Sometimes I store them pressurized, sometimes not.  They get sanitized again before they get filled either way.

[brewsumore]

I keep a couple new keg lids, some extra pressure relief valves, lid feet caps, and extra o-rings on hand.  And when I have a problem lid it goes into the "Use as last resort" bag -- gets swapped out.  And when I find a problem (crease, nick, bend) along the rim of the keg opening, I have done my best to bend it back to the desired shape.  The theory is to remove all the defective parts within my inventory (around 22 kegs) so that when one is brought into use I don't have any that leak.

I don't think that I have any ball lock kegs that require a specific lid.  I do carefully seat the lids, sometimes having to reverse the direction the lid sits to get the best seal.  And spray star san when setting the lid under pressure to check for leaks.