I was using my Ibanez RG250DX which is a 25.5" scale, and that one was tuned to an open C chord or something like that... pretty low. The main guitar was a Gibson Les Paul Studio (24.75" scale). Now that I think of it, his guitar kept on going out of tune too... Same with my guitarist from my last band who owned a Jackson RR3 (25.5" scale).
Given they didn't know anything about keeping in tune, and I did, my guitar always had the strings wrapped as many times around the peg as I could get them without overwrapping each other. I like doing that, because... well i'll be honest, I think it looks nicer lol. It takes me a while to get them stretched and all that, but my guitar stays in tune for months, even with whammy abuse. I don't recommend my method.
I'm also remembering that one time I tuned up the gibson for the guitarist just to prove that a proper setup will make playing easier and you'll sound better (OBVIOUSLY), but he thought I was being too picky and we just continued to sound bad for the rest of the time we were playing. He didn't get the concept of string stretching, and he broke strings faster than he could break them in for the initial first stretching.
There was also a B.C.Rich N.J. Beast that we used tuned to CGCFAD. That one was the odd 25" scale. We tuned it up once and never had to tune it again except when we changed strings.
My bass is a 34" scale and its tuned to CGCF. I make sure each string goes around the peg at least once (for anchor, not asthetics). I tune it up once a week depending on how much I play. I tune it every time I practice really, but it only needs to be tuned around once a week if i don't keep up on it.
So ummmmmmm, stretch your strings several times (be careful with the high E). I like 11s sometimes, and 10s after i've played on 11s for about a month. They both stay in tune for me, and naturally 11s are a little harder to play on. But both gauges stay in tune and take as much time as each other to stretch.