I got my parents additional cards on my AMEX when I was 21. They used it all over Europe which boosted my spending under FICO and they offered me a Plat. Put everything on it for 5-10Y and you'll be offered a Black/Centurion. $500K LOC at Prime +2% is unbeatable. Lots of turnover and they will boost limits to stupid amounts. $800 Concorde flights (mid 90s). Air/hotel packages like NYC -> Amsterdam -> London for $1200 all in for a week. Savoy Hotel for $300/night for a two bedroom. Crazy perks. Centurion Lounge (a lot were closed during COVID).