the main issue is you have to go down every 1-2 weeks if you shoot very often.
for my case:
I stay Pasir Ris and working at Changi, knock off at 5:30pm.
Rush to Tanjung Pagar from my workplace to NSC = 1 hour
Return trip = 1 hour
Next day, same thing rush to NSC to collect = 1 hour
Return trip = 1 hour
total time = 4 hours
Cost:
One trip = $6
total = $6 x 2 = $12
It would be fine if the NSC is next door of my house and can provide 10 minutes sensor cleaning anytime i want.
SG D600 users should feel lucky, in other countries you have to ship the camera to NSC. The shipping cost is on the user and the lead time is at least 1 week.
DIY is only 5minutes.