there ARE situations, where it is NOT necessary to optimize your model, just because you know, that the details are that low, that no one will ever notice a difference in performance
That is simply not true. You should always be keeping a stern eye on polycount. A model should always have the minimum polycount needed to meet design requirements.
And you should
always be aware that your initial polycount is actually going to be
multiplied during the actual rasterisation process.
Put another way... if your mod has only 4 models onscreen at once, EVER, then the maximum polycount, per model, should be 15,000. Why that ceiling?
15K, shading step: 15K
15K, smoothing step: 15-30K, depending on a host of factors.
15K, glowmap: 15K
15K, reflectionmap: 15-45K, because of tesselation
15K, shadowmap: 15K
15K, transparency: 15K
Grand total, triangles per pass: 120,000 triangles.
So, for 4 models, we have a grand total of 480,000 triangles per rendering pass... plus the mesh for the map, which if it's SM3, may also include a shader pass, tesselation due to water shaders (that's a huge number of triangles) and other crap going on.
Now, keep going... let's say our FPS is 60. 60 rendering passes need to be made. Let's be really nice, and rate the map mesh at 5K triangles, no shader passes, no grass, no trees, no smoke.
485,000 * 60 = 29,100,000!!! That is how many triangles are being shoved through the GPU, plus a huge number of shader calculations, textures, normal coordinates, and a bunch of other data!
To put this another way... the average polycount in NanoBlobs is about 1500 triangles. Typically during play, you'll see about 20 of them onscreen, max, if combat is really heavy. That is about 30K triangles, or
half of the load of your 15K super-robots. And guess what? They cause massive, chronic lag for most users with typical systems, if they have any of the bells and whistles on. On my rig, which has a pretty decent GPU (7800OC), I get about 23FPS when viewing full-on scenes of massive carnage, with shadows, reflections, and other stuff on. That's pretty good! And I only got to that point in the first place after months of work optimizing the mod for speed, because people complained so much about how bad the performance was
you can make more beautyful models with higher poly counts.
Yes, but it's definately a matter of "by how much, for how much cost". A 10% increase in polycount, from 1000 to 1100, can give you a much bigger gain, in terms of detail, than an increase from 10K to 11K can. 100 more triangles, at the low end, means that you can add a few new boxes, trimids, or simple columns to add a great deal to the detail and feel of the piece. At 10K to 11K, we're talking about very minor feature greebling.
In short... if you want to push out more polygons... build something that is as low-poly as possible, then add greebles, one small bit at a time. Weigh the artistic merits of each new shape carefully against the overall polycount. When you are near the spec. for the game engine... you need to make hard decisions about this- either lose some detail elsewhere, or not add any further. You should not just be, "but it needs this to be complete" at that point. If you didn't do drawings before you modeled your piece, so that you know what it needs to look like before you started, then you've just learned the hard way why almost everybody who knows what they're doing does so

Half the reason newbie modelers suck is because they just sit down and start modeling, instead of doing drawings until they have a hot design... then they end up with an unworkable mess
in my eyes your texture must be as good as the model
Bullcrap. Go look at models from old games. They are extremely low-poly, yet they worked because of the skins.
When you actually know how to skin, you will not ever say that again. You simply don't know what you're talking about.