The same conversations repeat themselves over and over again... as do the same pros and cons and reasoning. But I never hear anyone espouse my particular perspective (and I've said it many times.)
ks, consider this. You serve your master but never provide him with an outlet to just let himself go? He always has to read you and carefully tread that fine line that marks your day-to-day level of comfort? Why not gift him with a safeword you will use if he goes beyond your capacity to absorb... and let him freely use you without having to monitor you or himself. Let him revel in a release of his restraints and go explore his own limits as he uses you, with the knowledge that YOU will monitor yourself so that he can go farther than he might otherwise go.
Trust me. He's holding back. Perhaps not having a safeword and promising to use it is in fact, imo, selfish of the submisive or slave. Perhaps not having a safeword is an insidious way to maintain a level of control because it stops ones master from doing what s/he perhaps wishes to do.
Consider it a "present" to him. Like a birthday certificate. "My gift to you. A safeword that will allow you to use me without regard so that you can be all you wish to be today." Maybe you'll find it even more enjoyable than you expect. Maybe you'll find you can take more than you thought for him.
My girl has often said, "I was about to use my safeword and I thought... "wait just a moment longer" and that was when the endorphins really hit me and it got even better".
Better and much more satisfying for both of us.