[lojban-beginners] Not needing terminators

[Ian Johnson <blindbravado@gmail.com>]

I'm trying to work out when you need and don't need terminators. For example, here's a sentence I wrote today:
xu do se nandu lonu do tavla mi fo la lojban. lonu do tatpi
In idiomatic English, what I'm intending here is: "Do you find it difficult to talk with me in Lojban when you are tired?"
I put this sentence into jbofi'e and it appears to have parsed it the way I intended. However, when writing it, I was not sure if I needed to have a {kei} after {la lojban.}. I know {cu} makes it so you don't need terminators in situations like these, but what exactly makes it so that {lonu do tatpi} does not run into the {tavla} clause here? Is it that the place structure of {tavla} has now been exhausted (since I just filled the x4 place and there is no x5 place)? jbofi'e makes me seem to think this; changing {fo} to {fi} without adding a {kei} creates (according to jbofi'e) a rather nonsensical sentence in which {lonu do tatpi} is the x4 of {tavla}.

Also, just subjectively, is it somewhat..."polite" to include a {kei} here even though it's not grammatically needed? Certainly including every last terminator would not be, but where is the line where grammatically redundant terminators also became practically redundant?

mu'omi'e latros.