We’re testing some jobs in our test environment and orders entered with a required date of +4 weeks from now with jobs of 4 weeks in duration are all being scheduled with to start 1st NOV!
Hard to speculate without more details.
Times depend on many factors. e.g. your shop load, method structure, stock/nonstock mtls, finite/infinite etc…
I usually start by elevating the logging level(s) to see if those might provide any clues too. e.g. “MRP and Scheduling”