I had to upgrade from my SLI 780ti setup due more to there 3GB of ram was not enough then the speed of them..You may find some modern games like the vram hungry Rise of the Tomb Raider start to use your slower system RAM more so (depending on resolution/settings) compared to if you had a card with much more vram. This isn't a game breaking symptom of having less vram, but not ideal.
I Can't remember how much vram my gtx 1080 has without looking it up