Pruning Spirea

We learned in a WMMGA class that spirea can be pruned at any time.  I usually prune mine after they bloom, and I thought I was doing a good job pruning them back.  These pictures show, however, that even after a good pruning, they can get quite large again.  I haven't wanted to prune them back, though, because I'd be cutting off the blooms.  I guess I'll prune after they bloom and then once again.