If you are certain you can manage them entire, and they'll either finish well before the tupping season, or need until after Christmas, then you could leave them entire.
If they are likely to still be with you come tupping time, they will A. be a management problem if you don't have good fences

and B. stop growing, go backwards, while they are all hormonal.
jaykay you must have very good fences and gates you are very confident of - I can't imagine your farming neighbours being very impressed if any of your tup lambs escaped at tupping time!

(Which is why I daren't keep any of my primitive-type lambs entire unless I plan to use them myself

- none of our fields is secure enough for these agile little sheep if they are really determined!)