Let look at the flip side of rapid shooting - you can either melt the frensel lens or trigger the over heat cut off if the SB has one. Manual also suggest that you could blow the flash tube ...either of which would cost you about $200 to replace. Been there done that not funny. Funny how the later model SB800 is less robust than the older SB26 - so much for advance new technology.
For casual usage would suggest more set of alkalines or use the Panasonic oxrides - which offer significantly higher current and power capacity. So in theory 1 set at about $7 could be equal to say 2 to 4 sets of akalines.
Rechargeables are great if you use them constantly, not so good for the occasssional user. the bats should not be left idle for long periods. plus set up cost is considerable 4bats, charger will set u back abt $70 additional bats abt $15++++
there is a shop on the 3rd ? floor sim lim towers they sell sealed lead acid bats and the chargers for them - with a 6v bat some wires, some wood or plastic materials, 2 screws some soldering ect you could fashion a lead acid battery ala home made quantum without the frills my guess the whole thing could be done for under 50 bucks. down side lead acid battery is heavy abt 300 to 500 grams. Good for you are handy with tools and want some thing cheap.