Is it ever too late to start the probate process?

The short answer is no. Probate initiation is technically plausible for several decades. However, the longer you wait, the more complicated the process may become. For example, if an original heir passes away, then their inheritance would transfer to their own estate, and so on. You could also be subject to other statute of limitations (ie. Electing to take an undivided one-half interest in the homestead estate as a tenant in common must be done within 6 months). The sooner you begin the probate process, the smoother it will go, barring any disputes among beneficiaries.