10 years is long enough that you need to think about upgrade cycles. A cluster per year is fairly good way of approaching it because you can upgrade each one as you need to.
If you did that you could have an index per day without any trouble if you didn't subdivide. If you have different types of indexes then you should think about doing an index per week per type - but you need to be careful that types don't grow out of control. Sparsity vs explosion in the number of indexes is a thing to be concerned about but I think your plan is good.