How often should I wash a denim shirt (darker shade of indigo)?

So I got this embroidered denim shirt that's a solid dark blue (no fades or anything) and I was hoping to keep it that way as long as possible. I read somewhere that you should wash denim shirts as you would jeans, that is, as little as possible or around 4-5 wears. However, I kinda live in a tropical climate right now (and I don't wear a bra under my shirt sometimes) so we tend to sweat more here and often I sweat through (as in, you can feel the wetness if you touch it) my shirts as I sleep on the bus ride home. Should I wash them after 1 wear, especially if I've sweat through them even if they don't smell yet or should I also wash them after around 3-5 wears? Will denim shirts fade as much as denim jeans? The dark blue/indigo shade they have right now is really gorgeous.