My wife and I have recently committed to make long-duration clitoral stimulation part of essential sex as opposed to treating it as a short prelude to intercourse. I find I am so into her for 30-40 mins I completely lose my erection and feel totally relaxed after playing with her. I never have a problem getting a great erection at the start of sex, but after a long time paying attention to her it is surprisingly hard to reboot and get an erection going again. Is this normal ? Once we reboot everything is fine but when she is ready for intercourse she seems a little frustrated. How can I keep that erection going or restore it quickly if I spend 30-40 mins totally focused on her first?