I usually prune mine close to the ground, about 1/2 inch to 1 inch. Note: pruning the lacecap may result in no blooms from the pruned stems.

How many years will it take the lacecap to bloom after I
cut it?

Depends on its vigor and if you prune before it is time to produce flower buds (July-August). I have had hydrangeas that will wait one year before flowering again and others that appear to wait the following year. So if I prune them in April-May 2012, they have time to develop new stems & leaves and I may see blooms the following Spring or next (Spring 2013 or 2014). Below is a link with pruning and deadheading information if you are still curious.

Here is a link that might be useful: Pruning Information