Vet starts showing up in 1923, and stays for most of the first full sound season (I recall FARM FOOLERY) being his last, so maybe Spring 1930 he was out of VB? He went to Fleischer's briefly, and was probably out after 6 months, I think the only work he did that made it to screen was HIDE AND SEEK, a very held back title. I think his first at Lantz was THE STONE AGE, a July 1931 release. Backlot would've probably been six months so he probably relocated in late 1930 then

In fact, Farm Foolery was released on September 14, 1930, which indicates that he left the studio in the summer of 1930 rather than the spring. I note that he also animated the dancing walruses and the second barber bear scene in Frozen Frolics released on August 31 so I think it is unlikely that he left VB before the summer.