the evo is faster than the savage and cheaper
you do not need to worry about the lifespan ..i assure u if nothing is damaged the ssd can function beyond 5 years .
you can read this per example :
http://us.hardware.info/reviews/4178/10/hardwareinfo-tests-lifespan-of-samsung-ssd-840-250gb-tlc-ssd-updated-with-final-conclusion-final-update-20-6-2013 ( this 840 which is older than the 850 )
1 tib ( tebibyte ) = 1.09951 terabyte