My note 5 is not laggy and it's over 1.5 years old. It has never been laggy.
+1000
I'm just tired of the same comments and blanket statements from people that I really question their motives. I'm still waiting for the Lag and stutters on my Samsung phones and I've had Galaxy S2, S3, S4, S5, S6 edge, S7, S7 edge and S8+, that's just on the S line, and the Galaxy Note 4, Note 5 and Note 7 (this one obviously doesn't count). Of those, the S2, S4, S5, S6 edge and S7 edge were with me for at least a year.
I'm a phone addict, so I can easily have 4 or 5 phones most of the years but about 8-10 others, but that doesn't mean I get rid of my phones I just pass them to my family members when I move to a new one, and besides the S4 that lagged as a maniac after an update and never went back to normal, all my other Samsung phones have behaved the same than out of the box.
Like I always do, not just with Samsung but ALL my Android phones, I reboot once a week and at least once a month I clear Apps cached data. If I feel something is not as I expect, being battery life or any other thing then I do a Wipe cache partition on recovery Mode.