What’s next after 3 cards?

Hi all, looking for advice on the best “next move” with my Amex setup.

Over the last couple of years I’ve done the following:

- Started with Amex Gold

- Downgraded before fee

- Took out the BA Premium Plus (BAPP), kept it for ~1 year

- Earned the Companion Voucher, then cancelled BAPP after the year

- Used the Companion Voucher

- Upgraded the free Amex to Platinum, hit the bonus/earned the points

I’m leaning towards cancelling Platinum soon to get some money back via the pro-rata fee refund, unless there’s a smarter play. I’m not sure whether my partner even wants a credit card, but I could potentially refer him and start the whole process again. Do I need to keep my Platinum account open to refer him (so he gets the bonus/points)? If he takes out Gold, I could then close all my Amex accounts.