According to MSDN property
Specifies the limit for the input stream buffering threshold, in KB.
This limit can be used to prevent denial of service attacks that are
caused, for example, by users posting large files to the server.
By default for SharePoint 2010 it value is set to 50 MB:
<httpRuntime maxRequestLength="51200" />
According to SharePoint Server 2010 capacity management: Software boundaries and limits which describes software boundaries and limits of Microsoft SharePoint Server 2010:
Upload file size could be increased up to 2047 MB, however a large
volume of very large files can affect farm performance
According to the MSDN the
executionTimeout is a TimeSpan attribute that
specifies the maximum number of seconds that a request is allowed to
execute before being automatically shut down by ASP.NET
In SharePoint 2010 by default it value is set to 1 hour.
It value should be increased in case if "Request Timed Out" error occurs
[HttpException (0x80004005): Request timed out.]
,otherwise there is no need to modify it value.