Is there an optimal block size for current tape drives?

Once upon a time I acquired the notion that larger tape block
sizes yielded better throughput to the tape (subject to the
ability of the system to feed data fast enough.)

I've done a number of amtapetype runs on an LTO2 drive at
various blocksizes, and can't detect meaningful differences at
32k / 64k / 128k.  One run at 256k was killed for running too
long.

Opinions welcome.

Bryan