915 Turbo limits?

I have what may be a stupid question but I'm unable to find a direct answer.  

I understand the 5500 RPM continuous operating limit. And I understand the 5500-5800 RPM five minute limit. 

My question is this. My engine, on climb out, never goes over 5500 RPM (fixed pitch prop). Does the turbo have a time limit ? Or are there best practices being employed on the use of the turbo that people are using?