Should I update my late 2009 Macbook to El Captain?

I can only say that the most recent security updates are installed when you upgrade to the most current version of OS X. That is now El Capitan. Whether you wait or not depends on whether Apple still releases security updates for Mavericks, and if you are installing those updates.

k8allen wrote:

... it works great right now and I need it for classes, but I don't want it to be unsafe.

I would add to @Kappy's remarks by suggesting in the future, you not allow two years to elapse before considering whether to update/upgrade your Mac. Apple's software updates/upgrades tend to introduce new features and/or fix defects (including security issues). I suggest regularly applying them in the future as soon as they become available.

You could download the El Capitan installer and save it, such as the method

described in the DiskMakerX site; then later on, it could be used. -- In fact a

copy of the current OS X on the computer may be downloaded for similar

archive if the version now running, was acquired through & visible in the

App Store - when user owner ID logged in to App Store to see purchase list.

http://diskmakerx.com/whats-this/ -- http://diskmakerx.com/

OS X El Capitan - Technical Specifications

{A command-line method of creating a bootable installer requires more effort

and so may deter non-technical users; DiskMakerX is an easier way to go than

Create a bootable installer for OS X - Apple Support - instructions in terminal.}

Anyway you choose, be sure to create good backups and copies. A clone of

the entire present system on external drive may be an idea, especially if the

internal original hard drive is getting old or tired. Plus another for Time Machine.

A fairly good (yet slightly dated) reference...

• Apple OS X and Time Machine Tips:

http://www.pondini.org/OSX/Home.html

Good luck in any event! 🙂

Be advised that your 2009 MBP will be too old for the Sierra OSX. It is El Capitan or the status quo for your MBP.

Ciao.