Tim was it for me. I think Batman works best with Robin part of the status quo. Tim was Bruce taking all his lessons in mentoring and generally training the most rounded Robin who was likely to be his best successor. Every Robin and new protoge afterward has been diminishing returns.
I like others, but I won't pretend that every new child soldier in Gotham just eviscerates the stakes. Remember when Bruce and Dick trained for years, with Dick even coming with pre-installed acrobatics and mastery over fear? Characters are Robin level right out of the box now. It means nothing.
I think the reason I like Steph so much is because she was just not at their level and it made her compelling.