Yes, I think teaching your child to spend wisely will help him gain financial sense which will be helping him in his future a great deal. Though my child is still 5 year old, but I give her little money to have her an understanding of money and how it works. When I go to market I let her buy ice-cream for herself and exchange money with the vendor, so that she knows that she has given a Rs 50. Or I let her buy a packet of cookies and make her pay. And if she gets less money back, she gets sad that I paid the vendor bigger amount and gave less. ;)
But I think these things build financial sense in kids and should be encouraged. We in India, do not give practical knowledge to kids. I have met people as old as 25 who don't know how to open their account. So, I guess it says all. And we should definitely tach our children how to use money wisely and things alike, and 7, 8 years is good enough.