You need to prune in the summer to get new fresh growth , feed in the spring but sparingly only if the leaves are showing a yellow tinge or hints ericaceous feed is best.

Do you know what the variety is ? and the conditions its growing in would help to answer your question

Gg

It is because that is what they do, Tadpole. You can try hard pruning them or taking cuttings to replace the original plant, but many of us just let them grow until they get too leggy, dig them out and replace with a new plant.