I'm uncircumcised so I am biased, but there was one I got that took months to break in. It had a bunch of plastic nubs and also was kind of tight so it would basically rake your dick head. The first time I did actually get pleasure from it, I was frozen in place after using it because the stimulation was so intense. Even though that only happened one time, the burning sensation and needing to stop was the most common.
But it took months of using a soft onahole, and only switching to the hard one every once in awhile. But now the soft one is fucked to death so I have been using only the hard one. And i am used to it by now, I only worry how it would effect me with a woman. I have sort of been with one before, and I know the excitement level is higher.
So that would make a difference, but I just wonder, if I got used to her pussy would that be a problem? One time I was using it hard trying to cum and a cam girl said, "wooooow" I just don't know if a real girl wants that. It's weird because hopeless romantics believe women want 6 foot Chad's with 8 inch dicks, which they do. But at the same time i realize that she's not going to want to be rammed like that (every single time).
I weigh a decent amount and have a small amount of muscle from lifting 50 pounds boxes at work. Even though I know chad is muscle bound and plays sports and has a lot of experience with girls, really it is up to her. Because I am very sexually fucked up.