I’m roughly where you are career-wise, and I do still have some university pieces in my full portfolio. If they demonstrate something you have not been able or had opportunity to do professionally (a type of work or project, a particular skill), I see no reason they shouldn’t be there. Just be prepared to talk about why, because it will be noticed – why have you not been able to apply or adapt these things to professional projects, what do you like or feel is still relevant about this example to keep it in your portfolio, etc. I have been asked those questions in various forms during interviews. Or you might consider just doing some current ‘portfolio pieces’ to replace them – updated graphics, a new design using the same scenario, etc.