It is best to begin with about four guitars at least three with a tremolo *yours is a hollowbody, yes? where it carries its acoustical value AND a tremolo very cool As I play they need tuning periodically Reference is paramount Different songs carry different tunings as Artists themselves...
..hadn't considered any prior stretching ..can say, when one string is broken Id rather change them all if they are old.
I always stretch a new set of strings hard once I put them on and tune roughly to pitch. I saw guitar techs doing this backstage when I was young and took it as a lesson. If you give them a real good stretch then tune back up to pitch, you can be confident it will hold tune much better!