Nikon sb700 sb800 sb600?

I have a Nikon sb600 and a sb800, the 800 may be dieing. I shoot in a very fast paced heavy use environment, where quantity is way more important than quality. I need a backup flash, the sb700 is way cheaper than the 800 or 600. Any reason why I can't use the 700 to replace either? Your thoughts are appreciated. The 600 and 800 are coupled to Nikon d60.

The SB700 is only slightly less powerful than the SB600 or SB800, but it should work in most cases.

Also the SB700 has advanced thermal circuitry where it will slow down or reduce flash output if you are overheating it, so that as not to melt down during heavy use.

Or you can buy the just-announced SB910, which is supposed to have fixed the S900's overheating problems by incorporating the advanced thermal circuitry that is found in the SB700.