It's going to depend a lot on the destination.
A violinist or guitarist wouldn't want to take their instrument into the jungle for even a few days.
And the pianist...
If possible they would find somewhere to play.
I used to go to the Canaries a lot, and found some nice schools of music - with instruments, of course.
Went to Russia years ago, ended up buying a guitar to keep practising.
A lot of musos have at least one other instrument to play.
Often, I'll put a clarinet or flute into the suitcase, small enough, and quiet enough to use almost anywhere.
Depending on the destination, (and genre!)
there may well be a band, orchestra or open mic venue that could be explored even before the sojourn takes place.
You're right - an edge is usually lost with that sort of time away - trumpeter's lip, fluidity, reading, chords not so frequently played on guitar, but it soon (hopefully) comes back.
But most musos would want to have their dose of music at a frequent level.
And let's not forget, he'll have his music to listen to, and maybe some dots to follow on the Ipad.
music.stackexchange.com/users/2808/Tim
Most musicians take a small instrument with them when on holiday, but even if you don't, you still have your voice.
As long as you have a way to record or transcribe then you can still practice and learn.
I often find that a few days away from my main instrument really helps me change my improvisation structure, so I like to listen to a lot of different music on holiday.
That stuff I don't usually hear makes its way into my head and when I return it comes out in my playing.
music.stackexchange.com/users/104/Doktor Mayhem
If you're a serious professional musician you just DON'T take a day off practicing, let alone a month.
If your standards (or those of your employer) are lower, you just cope.
Yes, your playing will drop.
Yes, it will come back.
music.stackexchange.com/users/17003/Laurence Payne
The answer to this also depends on how bad you want it.
If you simply play as a hobby, it may be good to take a hiatus to return with fresh creative inspiration and yearning to play.
For the die-hard, there's so many options with modern technology.
For the pianist: Funny story: my mentor, in the days before the technology pictured above, made this little board with a 2 octave run of piano keys.
He had ingeniously carved the board and attached the keys in a way that perfectly mimicked a piano's action.
Of course, it didn't produce sound...
But, he constructed it for the explicit purpose of being able to practice fingering while on vacation/holiday.
He'd continue to use it after that - even driving down the road.
:P
Yo-Yo Ma buys an extra plane ticket for his cello when he flies.
A professional will sometimes ship their instruments to the destination, when they can't be carried.
One can almost certainly line up a gig or two in order to cover any transit costs (playing music is never 'work' for some of us.)
I have basses in the homes of select friends and family for when I visit, so I don't have to carry around my main squeeze... Or purchase something inexpensive at the destination, as Tim says.
music.stackexchange.com/users/32548/Tim Burnett - Bassist
I'm not a pro
but I have a cheap guitar and mini practice amp and headphones that I take with me, as well as a portable digital piano with a decent feel.
I do spend two weeks away from my main gear every year but again, I'm not a pro.
Also those two weeks I spend at the beach
but at a rental cottage that has air conditioning
so it's ok for wood and electronics.
music.stackexchange.com/users/6070/Todd Wilcox
let's say you wanted to take a 3 month vacation  How would you 'keep practicing?'  I mean you don't just forget everything but won't you feel like 'ugh' once you get back on your instrument?
what do musicians do if they want to take a vacation?
music.stackexchange.com
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music.stackexchange.com/questions/51478
music.stackexchange.com/users/32961/Lenny
Most musicians take a small instrument with them when on holiday, but even if they don't, they still have their voice. As long as you have a way to record or transcribe then you can still practice and learn. A few days away from an instrument sometimes help change motivation and things you do not usually hear may pop into your head, providing new ideas when you go back  Musicians go on holiday to listen to music they don't usually hear. When they return they find that the new music they hear makes their way into their heads. They often find that a few days away from their main instrument really helps them change their structure.
Most musicians take a small instrument with them when on holiday, but even if you don't, you still have your voice. When they return they find that the new music they hear makes their way into their heads. They often find that a few days away from their main instrument really helps them change their structure.