well, a thing I've learned the hard way, and is probably rule number one when making a mesh: optimize!
and optimize again, and again, and that's not enough, so optimize again!
never wondered why all those profesional meshes, when seen as wireframes, looked so clean, with polys as almost perfect quads?
it's not to make a pretty wireframe

most of the time I spend on my meshes is to clean them, remove useless polys, weld vertices, turn edges, weld other vertices, etc etc. it's long, it's boring, but it HAS to be done if you plan to do anything more than a stupid still render of your mesh alone, on a grey bakground. Well, the other option is to make both you and your computer bear useless slowdowns, memory access, etc etc.