Answer
This is the standard 30-minute timeout that applies to any interactive/online (foreground) process in IEE generally, not something specific to Migration Jobs or new to Apps10 specifically — any process run manually/interactively that takes longer than 30 minutes will hit this same timeout. Scheduled/Background Jobs have no such time limit and run until completion (or until they hit an actual error), regardless of how long they take. For any migration job (or other process) likely to run longer than 30 minutes, running it as a Scheduled Background Job rather than executing it manually is the recommended approach.