[Plugin: Jetpack] WordPress.com user account question

Hi,

I would like to try to use Jetpack on a client website, but I have a question about the WordPress.com account. After I’ve completed the site, I will have no ties to my client’s site, so do I need to create a WP account for them just for their site or can I always use my current account to connect different sites? If I use my account, if they ever need to change anything, will they need to get with me to do it because it’s my WP account? I don’t want them having to depend on me for anything once the project is complete. Still not even really sure why you need an account to use most of those plugins anyway.

Thanks!
Holli