That would probably be a good idea, and not so much because of the extra disk space. Free Hosting accounts are only restricted when they're new; you can request that the space restrictions be lifted if you're using more than half of the allowed space, your account is in compliance with the Terms of Service, and is more than 7 days old.
The reason I'd recommend going to a Premium account is because you actually need your site. One of the main drawbacks to a Free Hosting account is that you are sharing a server with thousands of other accounts, and not all of those other users are well-behaved or know what they're doing. So the server is doing a lot of work, and a lot of what it's doing is needlessly taking up processor time and memory. That can lead to frequent request time-outs and server glitches, meaning that you can't actually rely on your site working when it needs to. Throw into the mix the fact that you're using a couple of pieces of software that are, um, a bit on the portly side and could stand a little extra memory (RAM) space and processing power, and moving to Premium is almost a no-brainer (provided, of course, that it's not a hardship).
On a Premium server, your site will be there reliably and it will be many times faster than it can be on Free Hosting. (There's a 99.9% up-time guarantee.) You will be sharing a server with far fewer other accounts, and you will have access to more RAM memory and CPU. And because it's not free, there won't be nearly so many people "just trying stuff" that interferes with their fellow users.
