Folks say prune no more than a third of the size of a plant. I am not familiar with Mandevilla. Does it flower all summer?

It's a tropical vine that blooms summer thru fall here in Houston and can die back if we have an unusual winter. Until this past mild winter, mine died back to the roots and came roaring back, so pruning wasn't an issue until now. But, then, I have lots of vines and don't know how to prune any of them, since they get so interwoven as they grow.