There are several important considerations when you are trying to make your color last. It depends on the type of color you use: permanent, semi or demi permanent (aka gloss, glaze, toner) or highlights.
There are so many enemies to lasting color, especially in summer: sun, chlorinated pools, harsh shampoos; just to name a few.
Keeping your color looking fresh between touch-ups starts with your choice of color and the formulation. Colors that are no more than 2 levels lighter than your own natural color last the best. Reds are the hardest to keep.
The one thing that makes your color fade fastest is when you (or your colorist) refresh the ends of your hair with the same permanent color you use on your roots to cover your grays or to lighten and brighten. Permanent hair color contains ammonia. When you use that to refresh, it’s actually causing more fading. Always refresh your ends with a non-ammonia demi-color. It might cost more (at home) but your color will stay looking fresh usually until your next touch-up. At Vince Smith Hair Experience, we treat all our color clients’ hair this way. It keeps the hair really shiny and natural looking.
Always use a shampoo and conditioner designed to protect your color. One of my favorites is Redken Color Extend. Another that works really well is L’Anza Healing Color Care and Healing Moisture.
Cover your head when you are in the sun.
Don’t swim in chlorinated pools. Chlorine is what bleach is made of. It takes the color out really quickly.
Of course, all hair color does evolve over time. So you should expect your color to change and fade some. It should fade on-tone and not more than a level.