When I was 21 and at uni, I earnt extra money babysitting some kids of a couple that were good friends with my parents. The wife was quite attractive and around 40 years old. Once the kids had gone to bed, I was busting to go for a piss and went into the bathroom to find the toilet. After I'd finished, my cock was half erect due to the pressure placed on my prostate by my bladder. I was about to head out and watch TV when I spotted the dirty laundry basket and a pair of the wife's white panties. It had been about four days since I'd cum, so I thought it might as well happen tonight.
Her panties were still quite moist in the crotch; obviously, she changed to go out earlier that evening. I smelt her scent and her creamy pussy secretion and immediately got hard. I was careful to place the creamy crotch right over my cockhead while I masturbated, and the combination of her juices and my precum made for a great lubricant. I was soon spurting my seed into her panties, which completely soaked their crotch. It was a satisfying cum for me. I put the panties back into the basket.
About one month later, we met up at the shops. She said to me as we were parting that any time I needed help with a discreet release, I could come over on laundry day. I did take her up on her request later. She would give me a couple of pairs of soiled panties and I would go into the bathroom, do my thing, and leave.
I have no doubt she used them for her own masturbation sessions after I left.