How good is your game that you'd know if the strings are affecting it or not? Honestly, we know nothing about your true skill level and so forth.
If you don't know the answer to this question, I would say get a fresh set of whatever you have or something you know about from the forum that will work to your skill level (at least a decent synthetic gut), and get some play time on it. String it up mid-range if you don't have a tension you are sure you already like.
Create a baseline (not the one on the court) for a fresher string.
Can an old string (relative to a lot of factors, not just the "age" itself) affect "feel," "pop," and control? Absolutely.