This spin-up time raw value, a sign of failure?

Hi,
One of our hdd's makes problems as described below.
This drive operates always as external drive witin a hdd docking station and connects to host through USB3.0 or eSATA.
It is used as backup destination. It is a WDC3200BEKX.
It is set to GPT with two partitions, one formatted to mac os extended case non-sensitive, the another one to fat32 for max interoperability.
GPT and first partitions were created and formatted using os x disk utility. Second partition was created and formatted using Linux Embedded (NAS) and ntdos.fs.
After purchase over a time of some weeks it worked pretty well.

Problems appear in such a way that the os (ox s 10.9) reports frequently failures in partitions or other master/metadata regions.
There are also frequently probs on unmounting and/or ejecting from os x.

I wonder if these problems have their origin in docking station, in the hdd or the host machine.
In order to narrow it a little bit a SMART utility was started and extended test was conducted. One suspiecient point is the spin-up time reported by SMART: 733 raw value.
However the extended test completed with PASSED. Anyhow I wonder if this value is a sign of problems. Other parameters are quite normal.

Over all two further 3200BKEX, one 5000BPKX and two 5000LPLX are used. Amongst all those drives two show high spin-up time raw value (above 700).
What is your opinion regarding these high spin-up time raw values?