MSSql EXECUTE AS USER WITH COOKIE resulting in a memory leak - sql

Question

I need to use the command EXECUTE AS USER WITH COOKIE many times. After implementation, I was noticed that next calls (same) require more time for execution. To reset time execution helps only restart the SQL Server Service.
I wrote 2 simple tests multiple execution of commands:
EXECUTE AS USER WITH COOKIE
EXECUTE AS USER
Examples:
DECLARE #Loops INT SET #Loops = 1
DECLARE #CPU INT SET #CPU = ##CPU_BUSY
DECLARE #StartDate DATETIME SET #StartDate = GETDATE()
WHILE #Loops <= 3000
BEGIN
DECLARE #cookie VARBINARY(8000);
EXECUTE AS LOGIN = N'RestrictedLogin' WITH COOKIE INTO #cookie;
declare #ab varchar(MAX);
set #ab = convert(varchar(MAX), #cookie, 1);
REVERT WITH COOKIE = #cookie;
SET #Loops = #Loops + 1
END
PRINT 'ISNULL, both non-NULL'
PRINT 'Total CPU time: ' + CONVERT(varchar, ##CPU_BUSY - #CPU)
PRINT 'Total milliseconds: ' + CONVERT(varchar, DATEDIFF(ms, #StartDate, GETDATE()))
PRINT ''
and
DECLARE #Loops INT SET #Loops = 1
DECLARE #CPU INT SET #CPU = ##CPU_BUSY
DECLARE #StartDate DATETIME SET #StartDate = GETDATE()
WHILE #Loops <= 3000
BEGIN
DECLARE #cookie VARBINARY(8000);
EXECUTE AS LOGIN = N'RestrictedLogin';
set #cookie = convert(varbinary(8000), newid());
declare #ab varchar(MAX);
set #ab = convert(varchar(MAX), #cookie, 1);
REVERT;
SET #Loops = #Loops + 1
END
PRINT 'ISNULL, both non-NULL'
PRINT 'Total CPU time: ' + CONVERT(varchar, ##CPU_BUSY - #CPU)
PRINT 'Total milliseconds: ' + CONVERT(varchar, DATEDIFF(ms, #StartDate, GETDATE()))
PRINT ''
I noticed that for sqlservr process allocated more memory after each execution of EXECUTE AS USER WITH COOKIE command.
At the same time, sqlservr process's private memory not changed at all, after execution EXECUTE AS USER. And this example of code require a fewer time for execution (in some times between 3-100x).
To find the amount of private memory I have used the Performance Monitor
My question is -
How to correctly use the EXECUTE AS USER WITH COOKIE command without memory leaks and degradation time?