Once I tried stitch markers, I have become completely happy to use them! It can be done without, but if you want to knit comfortable, and the pattern is repeted several times, make it easy for yourself and use stitch markers.
You need not buy them (they are a nice present, however, if you want to give something to somebody who has already everyting), just a few short threads will do.
What do stitch markers do? They mark the spots where the pattern is repeted. So that you don't have to count, count, and recount.
What a relief!