To buy another set just so I can have the additional paint schemes seems like such a waste.
There's only a couple reasons why you'd buy more then one box.
1) You want 2-3 of each paint scheme, and don't want to do it yourself.
2) You want a squad of normal TI's, 181st TI's and ERG TI's, so you'd need 5 of each.
3) You want more copies of the cards that come with the set.
Other then that I can't see much reason to buy more then one box. You get enough cards with the box that you really don't need a lot of extras unless you can't proxie them.
If you want all 181st or all ERG, and already have some TI's, you could just repaint what you have.
If you want to use some of the named pilots, you can put a normal TI on the table, nothing in the rules would require that you use one of these alt-paint models with a named pilot.

