Oh Jazzy, considering you need 70 hours PIC in your 150hr CPL course, you'll find hour building beneficial.....and necessary.
Speak to your school though, they may have some requirements that you need to meet (such as only hours logged in their aircraft count).
Sorry, allow me to clarify: Should I build PIC hours now (before the dual CPL Nav flights), during (between Dual CPL Nav flights), or after (after completion of the CPL Dual Nav flights). Or does it not really matter when I start to build solo hours?