Tetenal's instructions give you a number of film rolls to be processed per liter of working solution. Depending on how much you mix (there's no need whatsoever to mix the whole 5l kit at once) you can work out the number of reuses. From personal experience and long time APUG reading I would say the instructions are fairly conservative in terms of possible reuse, but that BLIX and especially wash times can/should be longer than what the instructions say. You can hardly over-BLIX, but under-BLIXing has serious detrimental impact in image stability.