My veg cycle is only 16/8 or sometimes 17/7. I've often thought about a longer length just for reveg, I'm pretty sure it would help certain plants with reluctant genes. If I had a bigger operation.....
The biggest improvement I made in revegging over the years was learning to trim the rootball to match the top. That not only raises your average success rate a huge amount, but it also makes the actual regrowth happen MUCH faster. You can reveg in the same container the plant flowered in, but it's a lot harder (to water accurately, mainly) and with some genetics, probably won't work at all.
+ REP.
LUDA.