It's not so cut and dry as that, I don't think. Suian and Leane were only sworn under the rod for about 20-30 years right? Well when they were stilled and un-bound from the rod, who's to say they didn't lose 10 years or so? Un-bound we're talking about them living to 600+. You're not going to notice someone's appearance changing from losing 10 years on a 600+ span.

I hope this makes sense because I can't really think of an explanation to where you magically get your years back when you un-bind yourself. If you were bound for a 100 years then you've kissed 100 years off your life. Bound for 300 years? Well you just lost 300 years etc. Hence why it's tragic that Nynaeve swore on this rod because she's too good to give up over half of her life for nothing . Cutting Team Light's channelers life span in half is a good thing though right?

Last explanation on this as I understand it and set the age for this example at 600:

Bound channeler age 200 = ageless look, maybe grey hair depending on strength.

Same channeler unbound after being bound = appears to be a woman in her early 40's or 2/3 through her life. She will now live for another 200 years instead of a 100 since she's unbound.

Same channeler if never bound at 200 = appears to be a woman in her 20's.

So for a woman like Cadsuane who has maybe 20 bound years of life left at most, if she were to un-bind herself from the rod she would extend that 20 years to 40 instead. Magically gaining the bound years back would be incredibly cheesy and I don't think RJ would even attempt to sidestep the logic he created with the thing.