Double braid tends to shrink, not swell, with age, especially for halyards and mainsheets that have seen a lot of tension. This is especially true with the old Sampson XLS present on many of our boats. Putting a mic on the rope to measure it will give you 1/32" or 1/16" smaller than it should be.
On a related note, a woman writing in a boating magazine once said that men have an aversion to throwing away any rope. They will cast off jackets, boots, tools, any pieces of equipment but still save every piece of rope, no matter how mangy, they ever had. I happen to know this is true for me; and I suspect I'm not alone.
The best of luck to your retired halyards in their next role!
(Those old dead lines really came in handy during the Sandy storm when we needed everything we could find to tie down covers and secure gear!)