6 is a good age for a veiled. So much depends on the health of their bloodline and their care during their life that the lifespan can vary a lot. I've had one cham of that age and he did slow down quite a bit. He started to have some mild eye/tongue coordination problems but we never did pin it down specifically. He ate less, was less active but didn't lose a lot of weight. He passed away during a basking session.