I moved from a 22" to a 24" when I went to doubles because I couldn't look to my left without pulling the mouthpiece really hard. Whatever works and makes sense is the goal here, not a specific length, IMO..Soggy once bubbled...
Or watch me route a 7' hose...I'm 6'0", 150 lbs...I could wrap the thing around my head twice if I needed to. I now dive with a 6' hose and a 22" backup, which is perfect for me. Other people feel they need the 24" to move around comfortably. It all depends on how your hoses are routed and your personal size. 6' is perfect for me.