running degraded RAID to save power

[me-5yx05kfkO/aqeI1yJSURBw at public.gmane.org (Matthew Gillen)]

So I just ordered the parts to replace my home file server, and as usual I 
bought two identical drives with the intention of putting them in a RAID-1 
array.

Given a lot of the anecdotal evidence I've heard about identical drives 
purchased at the same time (thus likely to come from the same batch) failing 
very close to each other, I was thinking about a possible solution:

Set up the RAID-1 array with both disks, do the base install/configuration. 
  Then use hdparm to power-down one of the drives.  Have a script bring the 
drive up every few days and let RAID re-sync it, then shut it down again.

My thinking is that this will extend the life of one of the drives (in 
addition to saving some miniscule amount of power).

Has anyone tried something like this?  All the hdparm options dealing with 
powering on and resetting are marked DANGEROUS.  I'm not even sure that it 
can be done (specifically, keeping the kernel from trying to wake up the 
drive except when I want it to).

This is a home server, so a little (ie a week's worth) data loss doesn't 
worry me too much (compared to losing everything if both drives failed at 
once).  Or should I not even bother with RAID and use an rsync-based approach?

Thanks,
Matt