Size matters to an extent. Out of the four regular male companions my wife and I have had, Robert was about 50% longer than me. He was with us for about 6 months, but after he and Dawn had played for a couple of weeks, Dawn was a good bit deeper than before. She was like that when we first started dating and I recall the feeling when I would cum and we both could feel it "squirt" up inside her. We thought it was neat.
A couple of weeks after Robert moved out, Dawn's vagina had shrunk back down to fit me. So, I think for #5, we may be looking for someone longer again. We've not had any experience with someone noticeably wider than me, so I can't say about that.