When I first started being bottom any depth-girth-length hurt but eventually my hole got used to taking cock.That being said,a very long cock (longest I took was around 8,5 inches or 20-22cm) does not feel bad as long as your girl doesn't stick it all in at once.
Depth isn't really what matters most simply because our prostate is not too far in,in fact it's quite easy for an average or smaller penis to hit it.
Too deep can cause health problems like lacerations or air embolism but I'm talking about huge penises like Mariana Cordoba or Suzana Holmes.We're not pro so we should be careful with these sizes especially if we don't take dick often.
It also depends on your partners style,if a girl is too eager or sloppy she might hurt you even with a smaller dick.
Personally I get really excited when it hurts a bit because I feel my hole strech and that specific pain is pure pleasure,lube can make it heaven because you still hurt but you feel her rod sliding in and out and that can make you axplode in seconds.
