WprLoop.ps1

$wprBinary = 'C:\Program Files (x86)\Windows Kits\8.1\Windows Performance Toolkit\wpr.exe'
$wprDataFolder = 'D:\wprdata'
$numberOfFilesToKeep = 5
$localComputerName = [Environment]::MachineName

while ($true)
{
    "Starting..."
    & $wprBinary -start CPU
    "WPR started at " + (Get-Date).ToString()
    Start-Sleep 120
    "   Stopping at " + (Get-Date).ToString()
    & $wprBinary -stop (Join-Path $wprDataFolder ($localComputerName + "-" + [DateTime]::Now.ToString("yyyyMMddHHmmss") + "-WPR.etl"))

    $files = Get-ChildItem $dataFolder *.etl
    $oldest = $files | Sort-Object CreationTime | Select-Object -First 1
    if ($files.Length -gt $numberOfFilesToKeep)
    {
        Remove-Item $oldest
    }
}