Hand printed/painted leggings and t-shirts have a print that can last for years, since the ink is fixed ‘in’ the leggings/shirts and not on them (like with foil transfers). However, it is recommended to treat your hand painted items with care to ensure the print quality.
-ALWAYS wash inside out
-For the first 2 washes, wash by hand in cold water
-Use low temp washing program only (I recommend 30 degrees Celsius maximum)
-NEVER tumble dry hand painted/printed leggings or tees
-Iron leggings inside out
Beware; when washing light colored garments prints always fade a little. When you wash on high temperature (and yes, 40 degrees Celsius is too hot), prints might fade more than a little.