I'm wondering if there are any benefits to creating a runtime application that is used within the same company.

Specifically I'm wondering if there are benefits if the application needs to be updated.

I've created a solution for our equipment inventory that will be used (not simultaneously) by several users within our company.

I'm wondering if there is any downfall if something within the app needs to be changed or updated.

There's only one benefit to a FileMaker runtime: you don't have to pay for a FileMaker license. Runtimes aren't networkable, and whenever you need to make a change you'll need to deal with importing each user's data into the new runtime.

I take it you're on a budget. If it's only used by five or fewer people, maybe you could host your application with FileMaker Pro/IWP and the users would access it via web browser.