Reducing downtime for backups

I am investigating options for reducing the length of time that the system is
unavailable to users during our nightly backup job.  Not long ago we added disks
and started creating *SAVF files in a separate ASP for the backups, copying the
*SAVF's to tape later.  This reduced downtime to about 1 hour, but this
continues to grow as we add files and the existing files grow.  We are doing
full SAVLIB's using BRMS and have split out all of the program and non-essential
libraries into a separate job.  We backup 50 GB of data which compresses to
about 30 GB in the *SAVF format.  We are a single AS/400 shop running JD
Edwards.

At this point, the options I see are:
     Use SAVCHGOBJ.  We have done some tests on this and determined it will not
     save us much.  A large percentage of the objects are changed everyday and
     the system takes too long trying to figure out which objects to save.
     Separate "current" data from "prior year" data and store in different
     libraries.  We have already done some of this for the largest files.  This
     requires system changes because the users still need access to the prior
     year data.
     Use the Save While Active Option.  I suspect that this is the best solution
     and there is little (if any) out-of-pocket cost.  The downsides are a)  The
     time and risk associated with investigating and revising our current
     procedures, and b) Making sure that everyone here understands the
     implications of the new procedure.

I would be appreciative of other ideas anyone may have.

I have seen testimonials on this list that the newer tape drives are extremely
fast (we have a 3570).  They couldn't possibly be faster that going to *SAVF
files, could they?

TIA
Phil