On it's release, GTX 950 was low-end GPU. At today's standards, GTX 1050 is it's equivalent.
Here's what GPUs can do around 60 FPS:
GT 1030 - high settings @ 1024x768; low settings @ 1280x720
GTX 950 / GTX 1050 - low settings @ 1080p ; medium settings @ 720p
GTX 1050 Ti - medium settings @ 1080p ; high settings @ 720p
GTX 1060 - high settings @ 1080p
GTX 1070 - high settings @ 1440p ; high settings @ 1080p with 144 FPS
GTX 1080 - high settings @ 4K ; high settings @ 1440p with 144 FPS
Above list is more of a guideline than actual rule. Actual FPS depends on a game played.
As far as how long GPU lasts depends on your preferences. But in general and if you play latest games, GPU can last for 3-5 years before newest games become so GPU intensive that you can't play at e.g high settings anymore. Though, lowering in-game graphical settings would extend GPU usefulness but it would hurt the gameplay.