How long does a partnership dispute like this usually take to resolve?

Two to three years to actually reach trial is fairly typical for a genuinely contested partnership case that doesn't settle earlier, though the substantial majority of these cases do settle before ever reaching that point, most commonly once a court-ordered accounting has actually produced the underlying financial documents both sides need to realistically evaluate the dispute's actual value.

If resolving your specific situation within a period of months, rather than potentially years, is genuinely important to you, pursuing mediation, a structured, facilitated negotiation process with a neutral third party, before ever filing a formal lawsuit is worth serious and early consideration, since mediation can sometimes resolve disputes that would otherwise take years to work through the full litigation process.