Yes. It's prudent to have a second layer of security to cover any "holes" that might exist in one product only.
Malwarebytes has a good reputation, is highly recommended here,and is well known for interacting with MSE exceptionally well - I use both as resident programs and have never had a conflict.
If you opt for the FREE version of Malwarebytes, then you can achieve your monthly scan requirement, but....you will need to update the database manually and run the scan manually.
If you opt for the paid version of Malwarebytes ($20-odd for a lifetime licence) then you can install it as resident (it has a very low overhead in terms of RAM requirements in my view), you can opt to have the database update hourly (its a very quick update), and it also includes a very useful malicious IP blocker.
Whichever version you choose, adding Malwarebytes is definately, in my opinion, the best solution.
Post back here if you need more details.