Tautology: extensive periods of time [closed]
Solution 1:
Tautology is:
the saying of the same thing twice over in different words, generally considered to be a fault of style (e.g. they arrived one after the other in succession).
ODO, via Google
It is important to understand that a period of time can be any length, and your premise that 'a period of time' repeats the meaning of extensive is incorrect.
This also holds for 'extensive amounts of time', since amounts of time holds no indication as to the duration.