[R] survfit function?

[Terry Therneau]

Two thoughts.  First, prediction with time dependent covariates is
always an issue.  If you had unemployment as a month-by-month
time-dependent covariate in the first model, then for prediction you
will need to provide a month-by-month future unemployment scenario.
Doing this is easy in the code, but how to choose which scenario is
"relevant" and/or "interesting" is hard.  See section 10.2.4 of Therneau
and Grambsh for more discussion.
  Second, I think your time intervals will be ok.  Given what you know
now, the question is "will there be failure in the next 24".  I'd think
of "the next 24" as the time scale, and not a particular slice of
calander time such as "1/1/2003 - 1/1/2005"

Terry Therneau