Question

Useless question I guess, but accessing the property DateAndTime.Now computes each time the current system date and time, I suppose, is that right?

Thus it would be just a liiiiiittle better to favor:

Dim rightNow As Date = Now
For i As Integer = 0 To 1000
    If expiration < rightNow Then
        '   ...
    End If
Next

Over

For i As Integer = 0 To 1000
    If expiration < Now() Then
        '   ...
    End If
Next

Am I right?

Answer 1

DateTime.Now does a lot of processing:

public static DateTime Now
{
  get
  {
        DateTime utcNow = DateTime.UtcNow;
        bool isAmbiguousDst = false;
        long ticks = TimeZoneInfo.GetDateTimeNowUtcOffsetFromUtc(utcNow, 
              out isAmbiguousDst).Ticks;
        long num = utcNow.Ticks + ticks;
        if (num > 3155378975999999999L)
        {
              return new DateTime(3155378975999999999L, DateTimeKind.Local);
        }
        if (num < 0L)
        {
              return new DateTime(0L, DateTimeKind.Local);
        }
        return new DateTime(num, DateTimeKind.Local, isAmbiguousDst);
  }
}

It converts the utcNow to your local time. Because of the this calling is expensive. Depending on your requirements, the first sample will give you better performance.