This all started over ten years ago - my then-fiancee was going to chose her wedding dress and a friend, Angela, was going with her one Saturday afternoon. Her husband was going to come over in the evening for dinner and they were going to stay overnight.
I've always had a soft spot for Angela, and once the girls were off shopping I couldn't resist looking in the small overnight bag that Angela had brought with her.
All there was in there was a toothbrush and a pair of knickers. I couldn't resist the opportunity and wanked off in her knickers, filling the crotch with spunk. I then realised that I could well have landed myself in some hot water, but nothing could be done now and put the knickers back in the bag.
The thought and then sight of Angela walking around in those knickers the next day with my spunk rubbing against her pussy was amazing - kept me going several times.
Since then I've repeated this with several other women's knickers (all of them are sexy and could wrap their legs round my head any day) - always leaving them full of spunk in their knicker drawer or bat. I've always found it best if you can get a worn pair to smell whilst coming.
Go for it.