Jebus, it doesn't matter how many jumps it takes for Kirby to recover, nor does it matter how many ledge grabs he needs in an average match because Kirby is not causing problems. We don't make rules when there is no reason to do so. Remember: discreet, enforceable, and warranted. The fact of the matter is that grabbing the ledge is not broken. It's just not. In and of itself, no character breaks the game by grabbing the ledge. No character, in high-level play, is unapproachable on the ledge...
...with one, singular exception. A global ledge grab limit is nice and politically correct, but it breaks the criterion of being warranted entirely, because no other character except MK causes problems on the ledge, regardless of how and when they throw out U-airs. How many jumps a character has is irrelevant, because that's not what causes a problem. Having a great U-air isn't even a problem.
The problem is having multiple jumps AND a great U-air, AND a super-gimpy D-air, AND a glide, AND an invincible recovery move, AND 3 emergency recovery moves, one of which transitions into a second glide. No other character has that range of options and abilities, and so no other character causes problems on the ledge that can't be dealt with in some reasonable manner.
Global ledge grab limits are unwarranted, scrubby, politically-motivated rules that have no place in competitive Smash.