Verbal reduplication is not necessary if the second complement is a phrase expressing duration, frequency, or a goal. The duration and frequency can either be treated as a modifier of a noun or as a complement of the duplicated verb.
他打了好幾年的球了 (t¯a d˘a le h˘ao j˘ı ni´an de qi´u le/ He has been playing the ball game for several years.)
他寫了好幾次的論文 (t¯a xiˇe le h˘ao j˘ı c`ı de l`unw´en le/ He has written the essay several times.)
Reference: Chinese: a linguistic introduction by Chao Fen Sun