And then there is the long view
I well remember a conversation with a financial sector IT worker. We were upgrading the code on our Nexus 5k and his comment was along the lines of "we haven't gotten through testing the previous version yet". I asked how long it took them to go through acceptance testing and his answer was "about 3 years". When I asked why so long the response was "we like low risk upgrades where all possible failure modes are known and corrective measures tested and documented".