I am rated in various airplanes - but not current in them. Only one type.
At one time (1970s), I was current with two types at PanAm, 707 and 727...
This is the only time I flew both types.
I remember AA
did that a lot. But in more recent years they stopped the practice.
I remember a friend who flew both 727 and L-1011 with TW
The one with AA
was in DC-10 and 707...
Right now, my USA Licence lists 707-727-747-DC8-LRJET
My Argentina licence lists 737-747-LRJET. I am current 747 and Lear only.
To remain current on both, I must pass a check ride every 6 months.
First type this 6 months check, the other type next 6 months check...
If I have not had a check in a specific type in last 12 month, I am no longer current on that one.