Interesting stuff, due to my normal work.
(which is auditing and annual reports for companies.)
Overall exactly the same rules apply in the Netherlands.
I am missing something though, where I am sure this applies in USA as well!
Pretty hard to translate, but didn't you forget to deduct a percentage for yearly investments?
Let's say you buy a Solton for US $ 3000,--
I would write it off in three years, so deduct 33,3% of the investment each year, untill the value of trade in, and start writing off with the new then bought equipment and so on!
PC's I write off in two years.