You need to be a London borough resident. If you’re visiting from another city, sorry—this one’s for locals only. But if you live here, apply on your 60th birthday like it’s a ritual. Do it while blowing out the candles.
The card doesn’t expire even if you move out of London—but you must update TfL if you change your address. Otherwise, it’s a piece of plastic with no superpowers. Keep it active.
And one more thing: don’t lose it. Replacing it costs £20 again, which is annoying. Store it next to your bank card, or better yet, tattoo it on your arm. Okay, don’t do that.