Highs and lows or high and lows

The outgoing Chief Minister of Tamil Nadu, Jayalalitha, is one of India's most colourful and controversial politicians.
A former actress, her career has been marked by a series of high and lows.

In most cases the lows have been followed by dramatic political comebacks in which she has been re-instated as Tamil Nadu chief minister.

She has also been feted over the last 10 years by various Indian prime ministers requiring her political support to remain in power.

Her admirers say she has played a key role in the development of the state of Tamil Nadu as one of India's most economically influential states.

But the 58-year-old has throughout her political career of nearly two decades been accused of "acquiring wealth beyond her known means of income" and has briefly spent time in prison prior to her conviction for corruption in October 2000.


---------------------------------------------------------------------------------------------------------------------------------------------------


My question is on the second sentence of the above.


Shouldn't it be 'series of highs and lows'? I have learnt to write highs and lows; this implies bad times in sombody's activites to a certain extent.


I would like to hear from our experts.