Careful with placeholders though, they can give you a false impression of final framerate.
For example, if a character in the game is going to have 1200 polys, 50 animation frames and a 512x512 texture, then instead of using a primitive for a placeholder, make a realy quick crude crappy placeholder in your modeling program making sure it has 1200 polys 50 frameas of animation and a 512x512 texture. A cube for body, sphere for head,cylinder arms and legs, sub-divide couple of times. You can make one in less than 10 minutes, then when programming you'll be able to keep a realistic track of your framerate.
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