As you realise that’s a bit of a “how long is a piece of string” question....it’s a combination of EASA FTLs except where over ridden by the scheduling agreement (e.g 2 nights off before and after a long rangesector) complicated by the fact you can volunteer to remove some of the scheduling constraints...
The general situation is the company construct trip lines with a scheduling agreement Minimum Base Turnround of 3 local nights (2 clear days) between trips.
If a line has trips of high credit for days worked (“credit efficient”) there will be bigger gap(s) otherwise the final credit on the line would wildly overrun the Cap.
On some on the minimal time zone change trips (Northern Africa, similar) there may be options for the individual to volunteer at various points in the rostering/post rostering process to opt to cut time at base to 1 night, e.g. to “back to back”..useful when swopping.
Did that sound like a long way of saying “it depends”?
Apologies before hand if that’s a bit wish washy and perhaps not as definitive or illuminative as you’d like...
and then there's JSS................................