Keeping the software current on a Joomla website is imperative. There are security leaks in all software, and as they are discovered (hopefully before hackers discover them), Joomla Community addresses them with updates for Joomla installation, modules, components, etc. Yes, Joomla is free, public share-ware, but some of the extensions are not. They too must stay current.
I can't stress this enough. A website MUST be maintained. Would you buy a car and then never do any maintenance on it? Well, some would, but I doubt their cars would last very long. A company's reputation is only as good as their website. Doubt me? Ask around, check out Google, and see what you learn.
Maintenance and updates.... MUST BE DONE!!!