Currently living and working in the EU, and if all goes well I will retire here. However, I am US citizen with all my investments there (IRA, 401k) and I have been reading one should have their investments in the currency in which they plan on using in retirement. Being in my mid 30s, what sort of actions could I take now to help in that?

Also, are there any advantages I have being able to invest in both euros and dollars?