If I am having a convo w/someone that has been in the Lifestyle a while and has a general "understanding" of terminology and kink, I will use different verbage than if I were to have a conversation with someone brand spanky new to Lifestyle. I think that's only natural. You'd do the same thing regardless of whether it were Lifestyle, your favorite hobby, a situation in your home, something w/one of your kids/a spouse/a relative... you are naturally inclined to explain yourself at the level at which you believe you need to in order to communicate your point to the audience you are speaking with.
The problem comes in on the net, where you can't look at the other person or get in their head enough to know wtf their mind is thinking of, or know truly WHAT they know, or how much they know of it. It's great to hear "oh, I've been at this a while"---but that means a LOT of different things, esp. since the advent of internet BDSM.
Additionally, many people take terminology & use it when it's what they WANT to be rather than what they ARE. Whether it's because they don't want to admit it to themselves, or they want to give off a different external appearance... or... whatever... but it is what it is. Online, it's MUCH harder to "sniff out" the "truth" from the "fiction" in a snap--whereas in real life, I can tell in a heartbeat whether someone is what they say they are.
In other words, welcome to the internet universe.
This term, "no limits," is illusory as many have mentioned. The term is quite amorphous, really. It doesn't mean any one thing and yet it means a whole host of things. It's a common misnomer for abusive relationships, it's a common red flag for people looking for newbies in trouble, and, yet, it's also a somewhat-accurate term applied to many r/l 24/7 couples. So... which is it? When is it right to use? The answer? Really, anytime. It just isn't a stand-alone term, in my opinion. It needs some context. And, if someone fails to provide me context, I am going to lean towards thinking they are trying to "show off" or "make themselves something they aren't" rather than using it to really explain who they are.
All that being said, the comments here, I believe, are quite on point: yes, you can have people that have been in relationships a while, whose limits have merged w/their Dominant's limits to a point where it's a haze of "what is the limit, really?" You can also have the notion of "at some point, there's always a limit to what someone will do." You also have the "newbies should set stricter limits... know what they do & don't want to do... it helps to prevent bad situations."
I think the key is that people need to have discussions like this. It's ridiculous to assume that everyone is always "on the same page" or "understands eachother." We're a huge community. Why not take the 5 min to talk with someone and explain who you are, or talk about your situation, rather than simply saying, "yeah, I am a no limits slave to my Master." Don't you think that a 3 sentence description, albiet perhaps a bit verbose, might hit the spot more accurately? Since when did more words become crutches? I think in our quest to be inclusive, we've ended up starting to sell ourselves out to whatever lowest common denominator pigeon hole we can find, rather than truly saying who we are & what we stand for. I understand people get "tired of explaining themselves" to others. Ok. Then ask someone about THEMSELVES rather than talk about yourself for a day or two. Get to know other people. Or, stick it in your profile. Whatever. But the cop-out is simply that: a cop-out.
Just my two cents.