I have just noticed this post, and I "Liked" it right away.
I couldn't back the game while the Kickstarter campaign was up because I was out of job, and I must wait until I get my first salary next week to afford the $140 tier plus a few goodies (namely, the soundtrack on CD, the expansion pack and maybe the playing cards). I'm itching to pull the trigger because I have no idea for how long I'll be able to, and that's a bummer because the timing of my purchase does not depend on me — if I had had the money, I would have already backed Project: Eternity.
Moreover, I would really, really like to later upgrade to the $250 tier to have my collector's box signed by the devs and get ahold of the collectors' hardcover book, but with my Hungarian salary it's already a lot if I can get the $140 tier for now; the upgrade must wait till a later date. If the devs kept the tiers up and running for a longer time (in my specific case, let's say until January), I'm sure they'd get more pledges. Either that, or give those who pledged for a tier the option to purchase add-ons indefinitely, and add the collectors' hardcover book to the list of possible add-ons
Besides, I find it would be unfair to "discriminate" (quotation marks for lack of a better word) those who would have wanted to back the game but couldn't for reasons not depending on them.