I started leaving at least a couple of open spots on my weapons classes just to pick up the green engrams; every one you delete gives you glimmer and they are laying there right in front of you anyway. I would rather pick up the greens than the blues, because the blues will be waiting at the postmaster anyway. I became a glimmer hoarder since the heavy ammo drought and Iron Banner gear days, so I hate to get below 20K.