>>/64131/
You don't have to do 20h to do good normal training. If you can hold 40-60min of your ftp then what is the point of doing 2x12min ftp? Instead do 2x20min, then next time 2x22min, then 2x24min or whatever, you can still fit that into an 1h window. And if you are short on time, just do it all in one bout, 1x45min or whatever. Sweetspot, you need maybe 1.5h total – start at 2x30min, then 2x35min and so on, and if you're short on time then do all in one bout.
2x12min ftp or 2x20min sweetspot will get you nowhere, it's like doing 3x5x60kg in bench press if you can do 3x5x80kg