A lot depends on how the flash is being used. Are you shooting TTL in a well lit area and just doing fill flash? that means you get pre-flash with each shot and power levels are quite high. You will not get short recycle times nor many shots from a set of good batteries.
Last night I shot a wedding and did well over 600 shots using my SB-600 on a single set of NiMH Energizer 2650mah rechargeable batteries, and I changed them before recycle times even started to drop just becuase there was a lull in the action and it was a good time to swap them out. This was at a reception, and I was taking bursts of 6-8 shots in about 10 seconds and wait till the next batch. The flash was in manual mode and at 1/8th or 1/16th power, so I could do that all night. No preflashes and low power lets you do that.
That said, I have 4 Nikon speedlights that I carry with me to weddings and 3 sets of batteries for each flash. I do not believe in recharging batteries on location. Just grap a freshly charged set after one starts to drop and thats it. Lithium batteries may give good performance, but they are not as good as a good set of rechargeables. They are also expensive as heck and not rechargeable. Finally, they are bad for the environment.
If you do not want to ever run out, nothing beats a studio strobe set 13 feet high (near *any* will do)... I love my Photogenic 1000 W/s head set to 31 W/s, diffused and CTO gelled to 1 full stop. The effects are fantastic and recycle times are 1/10th of a second and since it is plugged into a wall socket, there are no batteries to replace or wear out!