Actually, even this probably wouldn't be necessary with today's drives and caching schemes where the hba will flush to the drives as fast as the drives can take it, which means it can probably get to their capacitor backed flash which writes it to nvram before it's an issue.
In general, you would want to boot up a server that suddenly and unexpectedly loses power, even if it is not used 24x7--just for it to recover gracefully. Then you can shut it down like normal without an issue.
I would expect super capacitor backed memory to last as long as battery backed memory if not longer, and I don't know if an hba implements nvram on the card to hold the flash data indefinitely (I would think some would).
And I guess it really depends on the card so I looked yours up.
You don't have to worry about a thing as yours seems to be doing the two stage cache protection of supercapacitor and nvram:
"RAID caching is a cost-eff ective way to improve I/O performance by writing data to a controllers’ cache before it is written to disk. In write-back mode, data written to cache is vulnerable until it is made permanent on disk. To avoid the possibility of data loss or corruption during a power or server failure, Broadcom off ers the CacheVault fl ash cache protection module or the LSIiBBU09 battery backup unit for the MegaRAID SAS 9271-8i controller. CacheVault fl ash cache protection uses NAND fl ash memory powered by a super-capacitor to help protect data stored in the MegaRAID controller cache. The RAID controller automatically writes the data in cache memory to fl ash storage when a power failure occurs, while the super-capacitor keeps the current going during the process. When the power comes back, the DRAM is recovered from fl ash storage and the system goes on without loss of data. Customers have the fl exibility to choose a traditional LiON battery solution or a greener, lower total cost of ownership (TCO) cache protection solution with MegaRAID CacheVault technology."
(from
Broadcom MegaRAID SAS 9271-8i | SSDworks.com)