I do it all the time. In fact, it's the main way I wash my hair if I'm not wearing braid extensions. Love how washing then drip drying makes the twists hang down straight. Love how the shrinkage gives my twists weight so that my fine hair actually can have movement and return to place after the wind blows.
I love how neat the ends become after a wash: instead of fraying out and looking wild, they curl up and form a neat end:
Some twists might unravel but most do not. After I wash, my hair is so easy to separate that I actually look forward to those that unravel so I have an excuse to play in my hair--coz I undo it, finger-comb and redo it. Freshly done twists always look so skinny and ugly to me (as seen to the right):
Old twists puff up and look full and just prettier to me (These are 8 washes later):
Besides the fact that twists on my stretched hair look so skinny and wonky and therefore ugly to me, there's also the fact that I don't like how they hang. I find the shrunken look has better shape and I'm comfortable wearing it out. I think if they were hanging a little lower, I'd have to wear them up all the time. Shrunken, I'm happy to leave them down.
The next photo is of my twists in 2004 on straightened hair (a little more than 2 years before my BC). I had no idea what to do with them. I tried putting rollers on the ends to give them a bob shape, but I still couldn't decide if that looked better with them being so spacey when left loose, or whether smoothing them down and pinning them flat was better. They had no movement as they were so light so just looked silly to me:
After I washed them, I was in love with them. Not just that they took a shape of sorts but they also became bouncy and alive:
Not only did I love that^^ look and the fact that they didn't look so "malnourished", but close-up the ends were so cuuuute! No longer fraying out and just looking wild:
Here's a more recent look of the way they hang shrunken--a look I love and hope I can hold onto for a long time. If they were not shrunken, they'd be hanging longer but lazily, having less of an overall "shape" and rubbing on my clothes--not to mention that now that I'm using S Curl on ends, I'd have product all over my shoulders
Below is a pic of my twists drip-drying after a wash--this is when I'm happiest in my hair-growing journey and most in love with my hair. Wash day is such a breeze. No detangling, no fuss, and that heavenly massage! Just shampoo (scalp massage), rinse, condition (or DC) applying relaxer style only on hair not scalp and squeezing to encourage conditioner penetration, rinse, ACV rinse dunk (scalp massage), finito!:
Riverrock asked about stretching them. As I stated, I really don't care to stretch them, but braiding them while damp and letting them dry in the braids does stretch them a bit.
In 2006, my hair was about as long as it was in 2004 and this is what a braid-out looked like:
And here's a recent photo showing a braidout on the back:
Also when twists are damp, they're easier to put into a style, so I always style my twists after a wash as they stretch easily. Of course you do have to be careful not to stretch them to the point of breakage since hair is weak when wet, but the coils are more flexible when wet than when dry so if I put my twists in a style, I usually keep them in that style until I wash them again so I can work on them when wet. I suppose if length is important to you, you could try banding to stretch them.
I also want to mention that twists will hold better if they are small since they are close to the size of the coils so that the bends sort of are in sync with the strand structure. So by wetting my hair after twisting, I allow the ends to form into coils that can be pressed together for a good "seal" until I want to undo them. I think doing twists on straight hair makes them not hold as well since they don't have the curves that help with the hold. I'm talking about 4B hair here.