I've just settled on saving for a ESP KH602 (kirkie hammie) and I've always had this poopie (but I love it) FirstAct guitar and I've never even heard of a locking nut on a guitar since I've never had a tremolo bar..

I've been reading it takes a longg time to change tuning, not that ill do it very often since Ill have two guitars, but how long do these locking system stay tuned for?

I'd really love to know this is intriguing I hate constant tuning..
Depends entirely on how much you abuse the trem, how well the guitar is set up, and what your sensitivity to "in tune" is. We can't give you a number or anything.

If you're cranking on the trem like a monkey, it's going to go out of tune. If you use the trem normally or even heavily (that is what the floyd/locking nut is for), you should be able to get through a few songs at least before needing to retune. Light or no trem usage will keep the guitar in tune indefinitely, barring ambient changes over the course of the day.
The bar up at the nut locks against the strings so that they don't move through the nut reducing or lowering tension. There are going to be fine tuners on the bridge where you tune the guitar. The fine tuners reduce and lower tension much slower than tuning pegs, which is why they are called fine tuners. Just google or youtube stuff about locking tremelo systems and such. Remember though, allen/hex keys are your best friend. You can't lock the nut without them.
On some guitars they go out of tune every time you hit the whammy. So you need to make sure you get one that stays in tune first. Then they go out as the strings stretch and/or the temp changes. But you use the fine tuners to adjust it back. Just like you use the tuning pegs on a non-locking guitar.
If the strings are fully stretched out and the guitar is set up right then it should stay in tune forever.

Or at least, for a long time. You will find strings go slightly out of tune, but with FR style bridges you have fine tuners on the bridge which you can use to (As the name suggests) make fine tune adjustments to the strings. But they should always be more or less in tune if set up right. Especially on better quality guitars. The 602 has a pretty decent FR on it I think, not sure if it's an OFR but it should be a reliable one.

Basically, as I've said, learn to set it up properly and you'll be golden.

EDIT. Geez, so many responses almost at the same time.
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If you're talking about with a floating bridge, I haven't had to tune my RR3 since I restrung it and It's been a month with maybe playing every other day.
You can drop it form say E to Drop D and get away with it but anything else will be a whole lot of calibrating the pivot on the tremolo. A floyd Rose has micro adjustments so you won't have to fiddle with the locking part often..

as long as the tremolo part is flush with the body it'll stay in pretty good condition.
There's a good chance that what I've written above is useless and if you take any of the advice it's your own fault.
Last edited by Silent Murder at Aug 22, 2011,
I don't think I've tuned in a few months

My Prestige just pretty much stays in tune.
I own a Ibanez RG370 for 6 years now. I always noticed that I didn't have to acually tune the strings(except fine-tuning a little bit). A few weeks ago we did a show a few miles from my hometown. And while we were soundchecking my main-guitar quited . So I went home to get my ibanez, wich i didn't play for more then a year. It really surprised me that even after 1 year i didn't have to tune that mother****er.