Been lurking here for some time and thought I'd give a brief story.
Past few late night romps, my wife has encouraged my to grind, external, on her dildos. She has a favorite 18" double dong that has quite the girth and a couple others that vibrate. Since I showed some pleasure, she also suggested I try it. I'm not shy in bed and will try just about anything so I bought some condoms (hadn't used them in ages) just in case since I wouldn't want to clean that mess up.
Last night was a lot of oral and the dildos got a good workout too. She asked if I wanted to try and after I pulled out the condoms she had her answer. Started with her purple g-spot. It slid right in and I trembled a bit. She was so turned on by my own sensations she began bouncing away on her 18"er and performed some amazing tongue action and moved the vibrator around and deep in me. I didn't know it could go so far! I have no idea how long that lasted but would have let her go all night if she was willing!