Will regular use of a whammy bar cause your guitar strings to come out of tune significantly faster than normal?
Yes, it will exacerbate detuning issues, sure, but a good quality tremolo combined with a locking nut will minimise this.
The main problems come from the movement of the string beyond the nut if you don't have some way to lock it, and slackening or stretching the strings.
Ways to minimise the issue:
- Get a good quality tremolo
- Use a locking nut, or if that is not possible a graphite or low friction nut
- Counteract actions you take, for example if you have divebombed your guitar give it a pull slightly sharp and vice versa.
It certainly can, but the impact it will have on your tuning depends on a lot of factors:
- How old your strings are
- What type and weight strings you use
- How solid your tuners are -- locking tuners will stay in tune better
- How deep you're dipping the whammy bar; big dive-bombs will put you out of tune faster
- How well you've stretched/broken in your strings if you've recently re-strung the guitar -- doing a few deep bends can help keep the tuning more stable while you're playing
One thing that helped me keep tune with use of a vibrato (both Fender-style and Bigsby) is using a tuning lubricant at the nut and saddle. Particularly with the wound strings, a deep bend can cause the strings to slide a little bit over the nut and/or saddle, and if they can't slide easily back into position, this might put you out of tune.
I personally like "Big Bends Nut Sauce" tuning lubricant, but I haven't done a lot of comparison. It was recommended to me by a local luthier. You put just a tiny but in each groove in the nut and each saddle when you re-string, and it really helps keep the guitar in tune (even if you don't have a vibrato -- it still helps keep in tune through deep bends and such.)
Careful setup of the guitar will help to minimise the effect that it can have. As mentioned by other answers, a good double locking unit will reduce the problems drastically, but even a fender style can work pretty well if you put the time and effort in. Check out this vid