All dyed fabric will fade eventually, from washing and sun exposure. Eco-printed cotton does fade more quickly than synthetically dyed cotton but there are a few ways you can reduce this to enjoy your fabric for longer.
I find that machine washing eco-printed fabric is fine, although I recommend hand washing for very special items. More important is to use a mild washing detergent. Most washing powders and liquids are too harsh and will quickly strip off the natural plant dyes. I use soap nuts, which can often be bought from health food stores or co-ops. Simply soak the soap nuts in boiling water for a few minutes, then add this liquid to the washing machine.
UV rays in sunlight will also fade dyed fabric over time. After washing eco-printed clothing, dry them in the shade or at least turned inside out. Bring them in as soon as they have dried and store in the dark. Also, try to avoid wearing eco-printed clothing if you will be in direct sun all day.
I have some eco-printed clothing that is still looking quite good after a couple of years of gentle wear. Once they become faded, clothes that have previously been eco-printed also tend to re-dye well. Re-mordant the fabric then dye as usual. Faint traces of the previous print can be seen on the cotton sample below, providing a lovely ghost effect.