Question: What should be the preferred way by programmers:

1) Only Write:

```
SomeBoolean = True

```

2) Read but write only if necessary

```
If Not SomeBoolean Then SomeBoolean = True

```

Answer: 
It's really hard to know the answer to this without knowing more about the environment. It seems a reasonable check would be to run some performance tests by iterating over this task many, many times.

Empirical evidence sometimes is surprising compared to what you'd expect.
The difference is negligible. You will see performance differences when reading and writing files to the drive, but program performance is measured in big O. Read:

[BIG O notation](http://en.wikipedia.org/wiki/Big_o_notation)

Especially in VB you will not see a difference.