Just like milk, your direct-to-garment ink has an expiration date. That date is not from when you get it but is from when the manufacturing facility produces the ink. Generally, for white ink, it seems as though there is about an 180-day window from production to when it is generally not advisable to use. Always check the expiration date prior to inserting the ink into your machine. Expired ink can cause problems with clogging and lead to expensive repair bills.
In addition, make sure that your ink is shaken up prior to use each day. This is a must, especially if your printer doesn’t have an automatic recirculating system for keeping the ink in suspension. If the inks separate out, you may not achieve a bright white ink laydown. Also consider that, if you leave ink in the printer lines for an extended period of time, it could also separate, or precipitate out, causing the same issue until new ink is introduced and fills the ink lines.