I update my VB from time to time.
My ACT1 VB was a bit pitchy and some of the oto.ni were off, so I fix that.
Every time I make my UTAU sing, I would find some problem and fix that; and over time, a lot of her phonemes and oto.ni would have been updated.
When that happens, I compress it for DL as ACT1.5 instead of ACT1.
I chose 1.5 instead of 1.1.0 because there was a lot of errors I fixed, and found no reason to name it 1.1.0 when I won't be fixing much other errors as it didn't look like it needed any more.
My initial plan was to record ACT1 and have Asuka be a bit "known" and hopefully get feedbacks. After I got some critiques, I would implement those into my later voicebanks ACT2 and up, and eventually when it is, say, "perfect;" I might stop at that.
When I recorded her voicebank, I didn't want her to sound human at all; in fact, I wanted her to sound like an UTAU-- like Teto-- robotic, kind of. This was because I planned on making a VCV (and possibly CV-VC, CVC, etc.) and her Soft, Strong, etc APPEND later on; which would feature her with more human-like features.
So in short, yes I update my UTAU('s) ovo~