As already mentioned, beware of high speed setups, as your internals WILL wear out quickly. Unless you know what you're going with internals and can easily replace the parts that WILL blow out.
Honestly, the rof you're more than likely getting now with that large battery you have is probably already putting some pretty heavy wear and tear on your mechbox shell and piston. I run a 9.6V 3800 mAh battery in both my M15 and HK 416 with more or less stock internals, and that's giving me 22 BB/s. Already that's a pretty high rof and it blew out the piston in my 416 last week.
And quite honestly, having such a high rof is rather useless. You want a gun, not a BB hose...