Fuel pump behaviour

[Forkie]

So the original, glass topped pump - if it starts an engine, idles, and drives - and the fuel flow and pressure checks out - albeit those tests carried out on the garage floor so to speak - one would assume that pump is ok, would it not? What i am asking is could a fault occur further up the rev range with it - so in other words because it does the above, and assume to be good, would it be good across all speed ranges and situations ? I am on the understanding the only REAL issue with them is diaphram wear/splits, which in that scenario would render it u/s until renewed or a rebuild kit installed.
I realise this is easily 'tested ' by simply changing the pump, but just thought i would see if anyone had any opinion on it.