A few decades ago mine was 8 1/2 inches when I was really excited.
Now it mostly stays hidden with only the glans protruding. I've seen FTM's with more down there than I've got.
Under rare circumstances it can get semi-hard and more than 5 inches, but it doesn't stay that way long.
Can I satisfy my wife? You betcha! Tongue and fingers can work miracles when you know what you're doing. After a few orgasms she will work on my choice of penis or breasts. I usually like her to work on my breasts. I can come, multiple times, from having my nipples sucked.
Randi