It isn't a smart strategy, or at least a cost effective one, to change the shutter just so to ensure that the camera is problem free.
For one, the shutter is one of the many things that may go wrong.
For two, the shutter is rated at 150,000. I don't have the probability parameters with me, but let's say the photographer regularly changes his shutter every 6,000 shutter count. It is likely that he would test it out, and the shutter would work flawlessly for the first few shots. I assume that if the camera should fail during an event, the shutter count would be about 1,000?
Then mathematically speaking, you are spending good money to avoid:
P(X<6000)-P(X<1000)
It is probably wiser and cheaper to get a second camera. Your probability is significantly lower because you multiply the probabilities. (Note: each probability is way lower than 0.01%, or a failure rather of 1/10000. Multiplying them will be even lower)
P(X<6000 "intersect" Y<1000) = P(X<6000) P(Y<1000)
Even after the 10th shutter change,
P(X<66000 "intersect" Y<1000) should still be reasonably lower than P(X<6000)-P(X<1000), or the replacing shutter every 6,000 shutter count strategy.
Assumption:
- the D300 is a good camera and variance should be low.
- the backup camera has a shutter count of 1,000 at worse, since it is unused
