Fresh strings reduce the risk of breakage and give you consistent tone and tuning through a set. In the studio, they usually offer better clarity, sustain and harmonic detail.
If your current strings are performing well, you may not need to change them. If they've become inconsistent or hard to tune, a new set adds confidence.
If you do change strings, give yourself time to install them correctly, let them settle, and make sure the instrument plays and sounds right before you start.