A lot wear their pins all the time. One told me it was his most expensive piece of jewelry. Another guy on my last cruise said he might only wear it at certain times as it got him a higher level of service, like to board. No one rule. I doubt I'd wear a pin all the time, but might at certain times.
I tip each leg. You will have different waiters and eat in a different place each leg. Even stewards change around it seems often so I might keep the same cabin but seem to often have a different steward. I tip a little each time i order a drink with a voucher, i dont wait for the end of the leg.