Seagate Cheetah woes

In an effort to keep up with burgeoning space requirements
I've been buying Seagate Cheetah 143 and 300GB SCSI SCA drives,
and replacing numbers of my smaller older Dec/Compaq/HP
drives with them. I'm now starting to see a rather alarming
failure rate for these larger drives, and wonder if others
have any good/bad experiences if them.
The drives in question are the ST3146807LC and ST3300007LC.

The tech specs on Seagate's website indicate an MTBF of
1.4 million hours (159 years). Some of my drives have failed
after a few months. I realise that MTBF means MEAN time-between-failures
and that one cant therefore expect them all to run for this long,
(I'd be happy with one-tenth of that) but with some failing
after a few months, I can presumably expect others to last
for 200 years...


Cheers,
Terry.