Really depends on the girl and my mood/ intent. Many BP girls would be 1/2 hr or less... wham, bam, thank you.. Others however I would prefer at least an hour if not longer. If Daty, MSOG, etc is on the table 1/2 hour is rushed. Plus some ladies like Riley, Gia, Felina, etc... are nice to enjoy a bottle of wine and extended flirting, foreplay.
It's like driving your car in the winter. If you're going to jump in and drive right away you're in for an awfully cold ride.