Saluton al vi, esperantistoj!
I was wondering if it was acceptable to add an affix to a root more than once. For example:
I honestly have no clue!
In general, yes.
My favourite example is from a story where a king said something like "Mi povas vin enkatenigigi!"
kateno = chain
enkatenigi = to chain up (en + katen- + -ig + -i)
enkatenigigi = to have someone chained up (en + katen- + -ig + -ig + -i)
So the king wouldn't cast the person in chains himself but he would order someone else to do so - so you have two "ig" suffixes in the same verb.
Theoretically, he could even tell his viceroy to order the prison master to cast the person in chains: enkatenigigigi. (But it starts to get ridiculous after a while.)
Yes, one can use affixes multiple times. However it wouldn't make sense in all cases. But "-et-" is applicable as many times as you want.