The old cards were intended to be kept for a number of years but I had many people asking for replacements because they had either lost them or their membership number had worn off. The new cards are cheaper and much easier because I don't have to write each one by hand. Also, with the old cards, I had quite a few people who quoted their membership number as "2014" as that was what was written on the sticker! Hopefully the new cards make things clearer.
If you have managed to destroy your card trying to separate it from the letter, ask your branch membership secretary to request a new one for you next time they send me some renewals or new memberships. If you are an individual member, contact me direct and I will send you a replacement.