I know the most common standard contract for idol groups is 7 years, but is that really necessary? Produce has shown that the short-term contracts have created some of the biggest superstars in Kpop and they're all on their own way to their solo careers. Many have became drama stars on the small screen, getting many CFs and ambassador roles and some are some of the biggest solo music artists of their generation. The others are all around in variety scene here and there, hosting radio shows or modelling work etc.
The standard 7-year contract is unnecessary and only holds the group for way too long in most cases. Shorter contracts give both sides more freedom and for companies, they're a way of "filtering" out the real stars from the fillers and allows them to get more money from the solo stars that the public has latched on to. Companies will only need to cater to one or two stars rather than the common 6-10 membered groups, cutting down a whole lot of costs and getting paid when the solo star go on variety show, acting projects or CF opportunities.