I guess it would depend on how tall they are now. Around here in the winter is a great time to cut them back hard if needed and they'll put out new growth in the spring. If you cut them all around to where there'll be no leaves left at all they will take a while to look normal again. Maybe 2-3 years.
They are pretty tough but you might get some dieback. When you cut them back you need to have an idea of what size you want them to ultimately be later. Take them farther than needed and plan on letting the regrowth form the new branches out to where you want them when you train them on subsequent prunings.