Is there a switch in Quartus Prime Pro to make it stop if routing hasn't completed within a certain time ?

Set it to 'Auto Fit' but that doesn't help.

Fast Fit is also not really an option since the design is indeed quite complex,

but with some seeds it places and routes fine (full implementation in 4-5 hours), while with other seeds it goes on forever trying to solve an unsolvable puzzle...

So a hard timeout option would really be nice. Is there somewhere I can submit this as a feature request ?