What is the Time Limit of Friendly Greetings in the Work Place?

I work in an office environment with 4200 employees. I have noticed that upon meeting a new person through projects, meetings, etc. that there appears to be a period through which it is acceptable for me to acknowledge the other when passing but that generally within a short time after the particular shared project or association ends most people will begin to ignore such acknowledgements. Is there an etiquette related to this that I am violating by still attempting to nod at these people when we pass in the hall? What is the acceptable time limit?

First off, do NOT allow other people's behavior to influence your own. That is how the world has slid into being such a rude place, one dirty look begats another and so on.

Nod or speak if you choose. If they don't respond, that is there problem, not yours.

piss on'em

Smile everyday at everyone, no matter if you know them or have worked with them. You will never regret that.

Some people don't want to be bothered. I stopped saying hello to my neighbors in my apt. building cause no one ever said it back. Basic etiquette is probably dead.

There is never a time limit on being nice.

Smile at everyone, or dont, its your call. If they choose not to respond, just know that you are the kinder person and you probably have more friends outside of work. They probably go home to a multiple cat household and drink box wine. Alone.

Sometimes when smiling and saying hello to my coworkers gets old I make a face at them on my way past. At least you stand out in thier minds, and that might count for something later on.

Just don't do what Elaine from Seinfeld did; that got ugly.

Just make eye contact first, some may look away meaning "don't bother me." While others may smile, then you smile back. Often, eye contact and a head acknowledgement followed by a "...g.morning.." will sufice. So depends on the respond after the eye contact.