If your aim is to get them to grow faster and bigger. Don't trim. Regular watering would encourage more growth.

If your aim is to create more density, then shear regularly.

Yes: removal of existing growth slows overall size increase. It really is true with shrubs as with other things that if you take part of it away you then have less afterward. This is because faster growing shoots made in response to pruning cuts do not immediately restore the total plant volume that would have been present if the pruning had not occurred. Let alone does the speed of their growth result in a bigger top than would have been present at the same time otherwise.

Once the previous size is restored then size increase resumes. What the cutting back produced was an interruption, a delay in a larger size being achieved. And not an acceleration.

The main reason for giving your box a top and sides every year would be to produce a formal effect. With each plant intended to be made thereby to appear as an architectural element.

Thank you Embothrium. That was extremely well written even in laymens terms. The new shoots that emerged on the tops was literally 8 inches higher than the rest of the shrub. Hence, I thought that maybe just giving them a shave in the spring would help the overall growth. Thanks for the wiki and the clarity

Edwards Scissorhands sighs just a little bit. I don't get to use my ARS shears alot, but it's a pure joy compared to my old Corona's