Well, the defective spelling is more usual in the Tanakh, but became rarer in later layers of the language. After the revival at the end of the nineteenth century there was a movement among intellectuals to impose a more "biblical" spelling with lesser use of helping vowel letters, so that וַ֫עַד־הַלָּשׁוֹן הַעִבְרִית, the predecessor to the Hebrew Academy, even insisted on defective spelling, when no niqqud was used. But as the Bible is not consistent on participles and even with niqqud mixed spelling like אָרוֹךְ and דִּיבֶּר instead of אָרֹךְ and דִּבֶּר became popular, spelling like הלך for הלוך have disappered and would now look old-fashioned even in fully vowelled contemporanean texts.
I believe that other synonyms, such as elderly, should be used for זקן/זקנה. I've reported it. My sentence, marked wrong, was "she doesn't run, she's elderly." At least in the English I know, it sounds better.