Before you order a new string, measure the brace height with the old string on. As Terry said, if you're happy with the way it shoots, probably no reason to change anything. However, the old string may have stretched, and you could be even more happy if you're shooting at the correct brace height.
If it's not at the correct brace height, twist it up until it is and then measure the string after twisting it up. If the old string is still shootable, shoot it at the correct brace height, and see if you like it better or worse than it was before you twisted it up.