FWIW, I got approved for a new Red while holding a White, which had been a Silver, which had been a Red, all within two years of the original Red being approved.

So to break it down, here are the dates:
Aug 2022 - Red Approved
Sept 2022 - SUB received
Feb 2023 - PC'd to Silver
June 2024 - PC'd to White
July 2024 - New Red Approved
Aug 2024 - 10k AU SUB received
Sept 2024 - Paid the AF today; I expect the 60k SUB soon (the AU bonus was received immediately after the AU made her first purchase).

All DPs say that with the Barclays Aviator cards, if you get approved for the card, you will be eligible for the SUB. I have not yet received the 60k SUB for the new Red, but I did get the 10k SUB for the Authorized User. The AF only appeared today, and I paid it today - I expect the 60k miles to land right away.

[EDIT: normally, you need to wait 2 years between cards with Barclays. But as my history shows, sometimes those dates are flexible. The only way you can know is to try - but two years between new card applications is a good target frequency. Remember, DPs agree that with Barclays, if you get approved for the card, you will be eligible for the SUB.

TLDR: The answer to your question depends primarily on how long ago you first got the Red, not how long ago you converted it to Silver.]