jeanne, I couldn't agree more with you.
For one scene or a few encounters, the limit/boundary discussion tends to be much more short and concise... you know what the scene is, so you really don't need to discuss everything. You just need to discuss enough to do the scene. It lends itself to probably a 10 min max discussion... are there issues? Usually not, if both people are clear. It is, after all, just a scene.
However, for a long term relationship? Much more. Think of it as an endless string of scenes... for every scene if you have to spend 10 min negotiating, think of the time you SHOULD be spending discussing things in a relationship.
But think about it beyond the "usual" limits. Most likely 80% of folks are "no" to kids, scat, snuff, etc... things that many people consider the "outer fringes" of kink (don't get me wrong... some folks consider scat a primary kink... and that's great too)... but what about kinks that will most likely "appear" in your relationship early on? bondage? what is your position on collaring? how about verbal humiliation?? People tend to "pass off" the "routine kinks" and only discuss things more on the "extreme" side... but why? It is important to discuss EVERYTHING.
But... if you are like me... talking things to death sometimes makes you have a migraine. Ok... then talk through certain things. Talk through important things. Then after each time you play w/your partner, talk about the session afterwards (not immediately afterwards, but after you've had time to digest it & think about it)... what worked? what didn't work? A good Dominant wants to hear these things. A good submissive should be communicating them. Why, you ask? Isn't it the Dom's just to "do the play"? No way! If the Dom doesn't know what the sub likes, or how the sub enjoyed/hated different play aspects, how is the Dom going to use the "right play" at the "right time"?
jeanne also mentions, and I agree with, the fact that there are many things beyond limits that you should be talking about. What's the relationship status? Are you both otherwise committed? What are going to be your o/l rules, say, if you are r/l but you both want to be in chat? What about posting on forums? Where do the r/l rules cross into o/l? Or, where do the o/l rules cross into r/l?
These are all sorts of things that just need to be discussed. The decisions aren't "good" or "bad"... you make the decision that's right for you both when you make it. Sometimes, things will change over time & you'll need to discuss different aspects of your relationship again.
But what floors me are the amt of people who go into relationships with NO discussion at all... where are the boundaries? How much do you want this person involved in your life? How much of your life are you willing to divulge, or give up control of? What impact will your relationship have on others living with you? Living away from you? What about your job? Other r/l responsibilities?
Whether you are o/l or r/l, you need to have discussions about things, or miscommunications will occur. And often, "blowups" in relationships are completely preventable if the pair would have had a sit down, REAL discussion about things. Now, don't get me wrong. I don't advocate a "whatever you want, Sir" approach to a discussion. You both need to be honest. Be on equal footing, have that real discussion. While, as Oz mentioned, it might cause you to lose a relationship, it will save you from an emo breakup down the road.