I farmed at least 4,000 exotic engrams during D1. Eventually, I lost count. One of the last times I played D1 I deleted a lot of them to make space for other things. There are probably still 50 of these engrams in the vault. I wish there was an easier way to obtain exotics in D2. I run all the lost sectors, and got another exotic helmet a few minutes ago, but this still is a very slow method to get what you want.