Our organization is running Oracle Forms 12.2.1 with Oracle Database 12.2.01; a small environment with 150 users and one interface. At current, we are in the process of scoping out an upgrade to Forms 14C and database 19C. Curious to hear other's experience with this upgrade and rough estimates of the time it took to complete. The plan is to acquire new hardware and perform an out-of-place upgrade.
For comparison purposes, our last upgrade from 10G to 12C took about 4 months to complete test and production environments.