meaning of "term extension"

when talking about renting an apartment, there are short term contracts and long term ones.
what is the name of this property that the “term” has? extension? duration? length?
if i want to write down a reminder to myself, could I write it as follows?
“do not forget to ask about the term extension”.

I would just use ‘length’. ‘Extension’ is inappropriate, since it suggests a change in an earlier term.