FRAMs are said to have effectively infinite endurance under usual application conditions. You may want to check the respective documents, to check if it's also true for your application. www.ramtron.com
FRAM is little costlier /density. You may also like to use Wear levelling technique. But that choice will depend on the cost benifit from the two solutions.
The AT45DB161B is an obsolete part - the replacement is the AT45DB161D. However, neither of those parts have an infinate number of read/write cycles. I beleive the 'D' part's endurance is 100,000 cycles.
As this statement is obviously contradicting your initial defined requirements, you may want to clarify your specification. The fact, that Atmel doesn't specify an endurance for Data Flash family does not imply infinite read/write cycles.
If you only need 8-32KBytes you could consider a battery-backed SRAM. Microchip has a couple (23A640/23K640 & 23A256/23K256) as does AMI Semiconductor (N256S0830HDA). These only draw a few uA in standby mode.