I've bee using the Klasse twins for a long time. AIO is not an equivalent to rejex as AIO is a cleaner prep and protectant all in one hence the name. SG is just a protectant. I know a lot of people who use AIO as a base for other products including Zaino. I use to do two rounds of AIO (just to ensure no missed spots) followed by 2-3 of SG.This would last a full year on my garaged vehicles. I rarely even get to the SG anymore I just top with S100 which is made by the P21S people for Harley Shops but cost less than 1/2.
As far as longetivity goes I got lazy this past October and slapped AIO on my pickup which stays outside all the time thru rain and snow. I still haven't hit it with anything else yet and it looks good and still sheds water.
AIO is great on pretty much any surface from your wheels to the windows. Brake dust rinses of my wheels 18 months after I did them. I used it on my glass shower stall as well a few other things inside the house.
Like most non carnaubas properly applied it only takes 1oz to do your car.
If you decide to use the SG I recommend really thin coats or wipe it on and wipe it off. I have heard people have problems removing the SG if too thick and you may need to hit with quick detailer to get rid of streaks.
