One of my majors was philosophy, and I started studying Latin before my Junior year, so I know where you're coming from. I think you'll find that a broad linguistic and classical knowledge will supplement your studies in unexpected ways.
I'm approaching my two year Latin anniversary this summer, and I'm happy I started as soon as I did. I've been studying Greek on my own intensively for about six weeks now, and I look forward to reaping the fruits of my labor. Mihi crede, amice, you're in the hardest part right now, and Latin will start to become a pleasure and not a chore after you've mastered the grammar and are at leisure to sip from the cup of Latin literature.
As for keeping your skills sharp, regular practice is key. I recommend getting a copy of Lingua Latina Vol. 1 by Hans Orberg, which you'll see is recommended perennially on this site. It'll reinforce and greatly expand everything you've learned in your schooling.
Nice. This summer will mark one year of Latin study for me. My school offered the the first two Latin classes (1010 and 1020) last summer, so I took advantage of the opportunity and took those two classes, which normally take two full semesters, in two months time. I just finished 2010 and 2020 a few weeks ago.
In the last class, we translated most of cena trimalchio from Petronius' Satyricon
. It was pretty interesting and definitely made me realize how limited my vocabulary really is. Coming from the safety of the Oxford Latin Course textbook, in which 85% of the words are straight from the vocabulary, it was a real kick in the pants to have to constantly be looking up the words that Petronius was using. It was very frustrating and discouraging.
I'm gonna check out that Lingua Latina; I've definitely seen it mentioned here a lot.