An interesting post on the subject of volunteering. While almost all the NGOs would prefer long term committed volunteers, even if few in numbers, the post advocates the benefits of finding episodic volunteers or as I understand, short term or one time need based volunteers who can still deliver value.
From brief, hands-on assignments to short-term, skills-based contributions, nonprofits can find many ways to keep good volunteers engaged without asking for big time commitments.
— Read on nonprofitquarterly.org/2019/01/07/microvolunteering-the-magic-of-engaging-time-strapped-supporters-in-meaningful-nonprofit-tasks/