Heat is what destroys clothes, not use. A hot dryer cycle does more damage to cotton fiber in forty minutes than a week of work does.
Wash cold, inside out. Cold water is enough for anything short of grease, and inside-out keeps the print off the drum. That alone doubles the life of a screen print.
Skip fabric softener entirely. It coats the fiber, which is the whole reason huck towels stop absorbing and fleece stops breathing. If it feels stiff, it's clean.
Tumble low or hang it. Low heat, pulled while it's slightly damp, hung to finish. This is the single biggest thing you can do and it costs nothing.
For grease: hit it with dish soap directly on the spot, work it in with your thumb, let it sit twenty minutes, then wash cold. Degreaser is made for degreasing. It works on shirts too.