Harvesting peas for next years seed.

Leave them on the plants until the pods turn dry.  The peas inside will be hardening into seed when the pods are yellow, but won't be fully ready.

 I find that if I leave them on the plant to dry, mice help themselves to the seeds, si I cut the haulm complete with partially dry pods and hang them up in the garage to dry off, or leave the pods on a plate lined with kitchen paper.

My site is well patrolled by neighbouring cats, so we don't seem to get many mice problems. 

I can sow peas and beans direct and not get them eaten, whereas I know Sunny has no end of problems on her site with voles and mice.  I guess that's the test - if you can sow direct, the maturing seed will be usually be OK, if not, harvest early.

I have ever hungry muntjac to contend with instead