i had 2 scarlet 3 infini apart every 4 weeks - Is it okay to take the last infini treatment? Or too much?

 I generally would recommend infini treats  4 weeks- 3 months apart, depending on the area. I would only recommend treatments closer together on certain skin types, if you are a fast healer or if you do not experience too much down time after your treatments. Your skin should continue to tighten  2-3 months after each treatment so I would continue to monitor for improvements over the coarse of the next few months. 

In my opinion, more treatments should yield better results. If you are healing appropriately, there should be no reason to not do your 4th Infini. I believe that if it is possible, doing the procedures as close together as 3-4 weeks will yield optimal results. This is due to the collagen producing inflammatory cells already being recruited and maximally stimulated in the areas of treatment.