Given that rubberdomes usually lasted at least several years for me, for the 'durability' argument to break even the mechanical keyboard would have to last at least 15 years. I highly doubt it'll take that long for me to fry it by spilling fluids on it... but we shall see.
I don't know why it's so weird to not bust your keyboard. It's not like FPS usage is all that hard on the keyboard. Admittedly I never used the bargain basement / prebuilt computer level of garbage keyboards (usually went with logitechs), and what might be a bigger factor was that when I played competitively was quite a while ago (my CS days were beta 3 - 1.6, when clanbase was still the center of the universe
). Back then
everything seemed to last longer. Mice would last me a lot longer back then too. When I went to university and became a filthy casual I think I had a Logitech MX518 that lasted me something like 7 years before it died. These days - even though usage is roughly similar - the mice tend to have either a broken scroll wheel or a broken button switch within 2 years (within the warranty period even!). Even when I gamed several times as much per day during my youth my mice (MS Intellimouse Optical / Explorer) would last longer than they do now...
I get that you want to at least have the placebo of not holding you back, but IMO that just argument can be just as much used against mechanical keyboards for gaming : the amount of accidental presses has skyrocketed since I went to mechs and it never went back to the old level. While I prefer the way they type, I think if I was gaming competitively I'd seriously consider going back to K120s for this reason alone. I think part of the problem for me is that the mechs are taller. Who knows, maybe it becomes less of a problem for me with the low-profile switches but I haven't tried those yet.
The fact that mechanical keyboards are on the rise has I think more to do with the fact that there's simply a ton of money to be made, and they have the coolfactor. It's not like RGB adds anything competitively but that has seen a meteoric rise as well.
If you feel it helps.. sure do it; a placebo effect is still an effect. I just think it's really really overstated, at least for FPS games. The higher rate of accidental keypresses alone for me nullified any advantage gained from better switches.