Is it just me or is everyone off topic here? The question is if the Note 5 will slow down, relative to it own performance, over time. Doesn't matter what you call it. However it is that you use your phone, will your phone be slower in "x" number of months compaired to how fast it was in the first couple of months.
One of the reasons that I have a Nexus 6P is because I anticipated the answer being yes it will slow down after a while. I don't know that that will be the case, but it was a factor I gave consideration when I decided to get the 6P. I had a niter for little I er a month and it is an amazing experience, it if it slowed down later on the up front honeymoon thrill is not worth of to me.