one thing to note is that, full Y (and all J/F fares) would actually earn you 1.5 points per mile. you can get Platinum for either 50,000 miles or 50,000 points, and Executive Platinum for 100,000 miles or 100,000 points.

so, your 55,000 miles of full Y flying would actually get you 82,500 points already. you only need 66,667 miles of full Y or J/F fares to get 100,000 points and you'll then be oneworld Emerald and get F check-in / F lounge access / etc.

that's exactly what I did, when back a few years ago my annual flying was more around the 70-90k miles range (but all in full Y or J), and so it's enough for CX Gold, or AA Exec Plat. I opted for AA Exec Plat for the F check-in and lounge access (besides the 100% mileage bonus etc of course).