I can only tell you my experience, and then tell you the recommended cross over.
If you look at ashton manual she has people take like 6 weeks to cross over from X to V. You can take a look at it if you wish, for me that was just too much time to cross over, i dont have the patience. My cross over was 2 days. I took half Xanax and half V. It wasnt very pleasant at all. I would recommend at least 7 days for a cross over to V. What i went through with just 2 days for a cross over was very broken sleep, a ton of anxiety and depression and feelings of just straight up fear like ive never felt before. It was pretty bad, but i did it. It took me about 3 full days of that before i started to level out. By 5th day i was fully assimilated to V and sleeping great, and feeling great. No more ups and downs, no more depression, just took it once a night around 9pm (10MG).
I plan on holding this pattern for at least 2-3 weeks before trying to taper because ive had 5 long months of suffering on Xanax and i feel so well now for the first time in forever i just want it to last for a while.
I also tapered off of V about 10 years ago, from what i remember yes it was easier than X but its still no walk in the park. I remember times when id taper and not feel anything, i remember tapering and couldnt sleep and felt like i had the flu and all bad things that go with it. There was no ryme or reason to it either. As you get lower in your taper the symptoms sometimes just pop up more because your cutting out more percentage. I did the 1MG cut every 10 days method, thats what i plan on doing this time to because it worked for me last time. I am a hard head though, and might not recommend that because its more than the 10% reduction they suggest here. Id rather be done with it than suffer for ever is why im ok with putting up with some really hard times to get to the end result. Its different for everyone though, youll just have to focus first on crossing over. You can dose Valium just once a day, 1.5 MG of Xanax is worth i think 30MG of Valium.
10 years ago i started on 30MG of valium and my Dr. started cutting me down 5MG every week. Looking back wow that was quite a cut, she didnt know what she was doing. It did get me down to 15MG before i hit a huge wall and had the benzo flu and felt horrible...thats when we stopped and i waited a few weeks to stabilize before continuing. Youll have to let your body tell you how much you can cut down. Remember that with V once you take a cut you have to wait like 3-5 days to feel the effects of it.