In article , Rusty Hinge
writes
The message
from Alan Gould contains these words:

The trick is to take the pods young and tender, then string and slice
them and have them into the freezer literally within minutes of picking.

The trick is to pick them before they require stringing.

Whether runners require stringing or not is a matter of personal taste.
I prefer to string even tender pods on both sides because though they
may not have developed strings, the sides are beginning to harden.
--
Alan & Joan Gould - North Lincs.