Hi,
In engineering terms this is called "creep", eventually leading to "creepiness"
Not really
Some materials are quite prone to this phenomenon, eg lead and some aluminium alloys, but not steels except at higher temperatures.
So, the main consideration for you at ordinary temperatures would be whether you are loading the parts to near the yield strength, where they might bend in an ordinary way.
Taking an EQ5 balance weight shaft as an example (probably chrome plated mild steel or similar), 250 mm long and 20 mm diameter, stuck out horizontally, you would need to pile on about 80 Kg of weights before things began to get creepy.
In short, no problemo
Cheers