I want honest opinions on this, does anyone use full-blown OOP, n-tier development for EVERY application they write?, if it is required from the analysis.

Analysis using UML defines a very strict OOP application, but I feel sometimes it's serious overkill for certain apps.

What I want to know is, do you draw the line at some stage, what if you KNOW that your app is only a one off, and will never grow? Or at least be certain of it.

I want some opinions, as I believe that there is a line between the practical and theory on this, which programmers can happily follow, whilst still following general principles.

Thanks
Kev