max time limit for solve



It is certainly possible to do this in some particular lisps, but it may 
not be possible to
do this in EVERY lisp, and certainly not using the same code in each lisp.

But you are asking for the wrong thing, in my opinion.  Why not
run_with_limits(  ----ANY maxima command---,    time_limit=..., 
memory_limit= ....,  .....)