Every time you ask someone for feedback, they're going to point out a different thing that you could do differently. Fix that and show them again, and they'll find something else. And someone else will tell you if only this one this was different (which is pretty much the way you had it before you listened to that other guy's feedback) then it'd be better.
Sound confusing? Because it is.
Most of my classes for my English degree in undergrad were poetry writing workshops and at the end we had to present a final portfolio with fully revised, near-perfect poems (little did I know how much it'd prepare me for portfolio school.)
I always put this quote on my cover page
"A poem is never finished, only abandoned." - Paul Valery
Left to my own devices, I'd still be working on some of those poems. Changing a the to an a. Adding commas. Deleting commas. Putting my right foot in. Taking my right foot out. Shaking it all about.
It's a vicious cycle. (That repeated itself all through portfolio school. And now sometimes at work.)
So while you're working on your portfolio now, keep working. Keep pushing. Keep making changes and seeing how they look, how they feel, how people respond to them.
* Always save each version with a new version name. You never know when you might need to go back.
* Write down all feedback you get whether or not you are going to use it. Look and see what trends arise. If two or more people say the same thing then you should probably make that change.
* Play creative Jenga. Take away one thing and see if your ad still stands. Then take away another thing. And another until it is at its simplest, purest and more straightforward without toppling over. (This is what you should aim for in most of your work. I see too many ads that are overdesigned and overwritten and overthought. The simpler the better.)
And know that there will come a time when you're just going to have to say "Okay, pencils down" and abandon your portfolio. (Only for a while though, because it may get hungry, or sick, or lonely. Or think that you don't love it and get depressed and take drugs and become a stripper. Nobody wants their portfolio to turn into a stripper.)