You've got the wrong forum, I think. You said you were using func_details, which are nonexistent in the HL1 engine.
Anyway, if you actually are using HL1, then it could take a long time if the map is really expansive. But if it's taking hours (or even 30-40 minutes), then you've probably tried to do what we warn so many people about not doing in HL1: Making gigantic outdoor areas.