Lets look it in this way:
The delay is wrt through line std. Through line length is considered to be of zero length ,with both reference planes overlapped.
Now the delay lines must provide phase delay in the range of 30 deg to 150 deg wrt through line.
So,if through line is of lambda/4 length,delay lines must be lenghthier .
One delay line must cover a BW 5:1,i.e. if frequency range to be covered is 1-10 Ghz,then two lines are required 1st will cover 1-5GHz 2nd line will cover 5-10GHz.
So,if line is designed to be 90 deg for center frequency,then it will provide 30 deg delay for lowest and 150 deg for the highest frequency.
In your case one delay line is enough.