Do lashes need a break?
If the sets were applied with proper isolation and at a weight your natural lashes carry, no. Extensions do not stop lashes growing and the cycle continues underneath exactly as it did before. Somebody wearing extensions continuously for five years with good work has the same lash line they started with.
If something has gone wrong, yes, and the honest length of it is two months rather than two weeks. A natural lash lives six to eight weeks, so anything shorter than that is not a break, it is a gap.
How to tell which you are in
You do not need a break if your sets last two to three weeks, nothing hurts, and your bare lashes look the same as they did a year ago.
You do need one if you have had pain or pulling, if there are visible sparse patches, or if your bare lashes are noticeably shorter and finer than you remember. All three of those are signs of poor isolation or excessive weight, and both of those are studio problems rather than extension problems.
What to do during one
A lash serum, if you want one. Peptide-based rather than prostaglandin: the prescription kind works better and can darken the iris permanently in some people, which is a real trade rather than a scare story.
A clean lash line and cuticle oil on the lid at night. And genuinely nothing else; there is no product that speeds a growth cycle up.