Improve performance of powershell script

I am using following Powershell script to break the folder permissions inside the Record Libraries:

    $webUrl = 'http://intranet'
    $web = Get-SPWeb $webUrl;
    $SPBaseTypeDocumentLibrary = [Microsoft.SharePoint.SPBaseType]::DocumentLibrary
    $lists = $web.GetListsOfType($SPBaseTypeDocumentLibrary);
    foreach ($list in $lists)
    {
    if ($list.BaseTemplate.ToString() -eq "1302")
    {
    $folders = $list.Folders
    foreach ($spFolder in $folders)
    {             
        # Add claims to folder
        $folderName = $spFolder.Name
        $spFolder.BreakRoleInheritance($false);
        $claimToken = "c:0-.t|clientcontracts|" + $folderName
        $claimUserDisplayName = "Claim User " + $folderName  
        $roleAssignment = New-Object microsoft.sharepoint.SPRoleAssignment($claimToken,"",$claimUserDisplayName,"")
        $roleAssignment.RoleDefinitionBindings.Add($web.RoleDefinitions["Read"]);      
        $spFolder.RoleAssignments.Add($roleAssignment);       
        $spFolder.Update();   
        }        
        }
       }

       $web.Dispose()

The issue is that the script is gets very sluggish. I have about 100 Libraries and each library contains 1000 folders. Is there any way to improve the performance of this script? How can we break permissions of folders in batches?