End Goals

You need to look at any project in its entirety as a system. What is the end goal for all your work really intended to be? In a large corporation or large collaborative effort, it is always best to stick to rigid standards and methods because so many people need to understand the different parts of the system on an indefinite and ongoing basis. The tradeoff in system inefficiency is (usually) made up for in organizational efficiency across the whole of the group or corporation.
For a project which will always involve a small number of people and resources; what difference will it really make if you rigidly stick to standards as long as the deviations are well documented and there is good communication between developers?
On the other hand, if the end goal includes selling or turning the system over to another group or person someday, having adhered to standards whenever possible will be a huge selling point.
For any project — What is the end goal and what resources are you willing to commit to achieve that goal?

There are reasons for conventions, but sticking to them for conventions sake alone when your overall goal is unaffected by these reasons might be counterproductive toward that goal in the end.