The greatest quality of acrylics is also the biggest problem, they dry too fast. There are though ways to keep them moist and workable for a long time. You could use a water spray bottle to spray your palette every 15 minutes or so. You can also use a retarder to keep the paints workable. But best solution I tried so far is a home-made stay-wet palette. You need a plastic box with a fitted lid, paper towel and greaseproof paper (baking paper). You can use a large food container.
Cut two sheets of paper towel and one sheet of greaseproof paper at the size of the box.
Place the paper towel at the bottom of the box and soak it. Drain off the excess water.
On top of this, layer a slightly larger piece of greaseproof paper and gently press all over, so that it makes contact with the paper-towel layers beneath it.
If you put the lid on at the end of your painting session, the paint can last wet for days, as long as the paper towel is wet. Good for breaks too. Be aware that in extended period of time the paint does gradually become watery.
Don't store your box in the fridge as it can ruin your paints.