ADO.NET, optimize code, writing to a sql table

Hi forum,
first a big picture: I've got a csv-file with app. 500 Servers.
The task is to: connect to every server, collect all user-accounts having anything to do with SQL-Server services.
Then loop the user-accounts list - only if it's a domain user -  and using Get-ADUser get the information about the account as: PasswortLastSet, Expiration etc. Then write all the informations to a sql server table.
I've got the first (working) draft. What I don't like is: in the time I'm collecting the data the connection to the sql server is whole the time open (it takes about 25 min. to accomplish the task..). I suppose I could: put the information termporarily in a csv-file and after complition read it back and then make insert in the table and delete the file. But it's not that cute. Maybe to create a DataTable, an ArrayList or something?
Thanks for your help.
Purclot
the code:

If(-not(Get-Module -Name ActiveDirectory))
{
    Import-Module -Name ActiveDirectory
}
# Open SQL connection (you have to change these variables)
$DBServer = "mySQLServer\SQL01"
$DBName = "Central_Management"
$sqlConnection = New-Object System.Data.SqlClient.SqlConnection
$sqlConnection.ConnectionString = "Server=$DBServer;Database=$DBName;Integrated Security=True;"
$sqlConnection.Open()
# Quit if the SQL connection didn't open properly.
if ($sqlConnection.State -ne [Data.ConnectionState]::Open) {"Connection to DB is not open."
    Exit
}
$sqlCommand = New-Object System.Data.SqlClient.SqlCommand
$sqlCommand.Connection = $sqlConnection
$servers = Import-Csv -Path C:\Users\XXX\Desktop\Get-ExpirationDates\Liste.csv -Delimiter ","
foreach($server in $servers)
{
    try
    {
    $accounts = gwmi win32_service -ComputerName $server.server_ip | select name ,
        @{N="Startup Type";E={$_.StartMode}},
        @{N="Service Account";E={$_.StartName}},
        @{N="System Name";E={$_.Systemname}} | where-object{$_.Name -like '*sql*'} | Sort-Object "Name"
    }
    catch [System.Exception]
    {
        ("win32_service error, Server: " + $server.server_name + " " + $_.Exception.Message) | out-File -FilePath C:\Users\W9A01RG9\Desktop\Get-ExpirationDates\Errors.txt -Append
    }
    foreach($account in $accounts)
    {
        $dbviewID = [int]$server.dbview_id
        $serverName = [string]$server.server_name
        if($server.instance_name -eq "")
        {
            $serverInstance = "DEFAULT"
        }
        else
        {
            $serverInstance = $server.instance_name
        }
        $sqlService = $account.Name
        $accountName = $account."Service Account"
        $splitter = $account."Service Account".Split("\")
        if($splitter[0] -like 'ww*')
        {
            $output = ADPasswordExpiration -SamAccountName $splitter[1] -dns $splitter[0]  
            $isDomainAccount            = 1 #isDomainAccount
            $passNeverExpires           = $output[2].PasswordNeverExpires
            $passLastSet                = $output[2].PasswordLastSet
            $passExpired                = $output[1]
            $expDate                    = $output[0]
            $accountCreated             = $output[2].Created
            $accountDescription         = $output[2].Description
            $displayName                = $output[2].DisplayName
            $accountSN                  = $output[2].sn
            $trustedForDelegation       = $output[2].TrustedForDelegation
            $trustedToAuthForDelegation = $output[2].TrustedToAuthForDelegation
            $sqlCommand.CommandText = 
@"            
            SET NOCOUNT ON;  
                INSERT INTO dbo.AccountsInventory  
                (DBViewID, SQLServerName, InstanceName, SQLService, AccountName, isDomainAccount, PasswordNeverExpires, PasswordLastSet, PasswordExpired, ExpirationDate, 
                AccountCreated, AccountDescription, DisplayName, Account_SN, isTrustedForDelegation, isTrustedToAuthForDelegation)  
                VALUES ('$dbviewID', '$serverName', '$serverInstance', '$sqlService', '$accountName', '$isDomainAccount', '$passNeverExpires', '$passLastSet', '$passExpired', '$expDate', 
                '$accountCreated', '$accountDescription', '$displayName', '$accountSN', '$trustedForDelegation', '$trustedToAuthForDelegation')"@          
            $sqlCommand.CommandText                  
        }
        else
        {
            $isDomainAccount =  0 #isDomainAccount
            $sqlCommand.CommandText = 
@"
           SET NOCOUNT ON;
           INSERT INTO dbo.AccountsInventory(DBViewID, SQLServerName, InstanceName, SQLService, AccountName)
           VALUES ('$dbviewID', '$serverName', '$serverInstance', '$sqlService', '$accountName')                        "@             
           $sqlCommand.CommandText              
        }
        try
        {
            $sqlCommand.ExecuteNonQuery()
        }
        catch [Exception]
        {        
            ("sqlCommand.Execute error, Server: " + $server.server_name + " " + $_.Exception.Message) | out-File -FilePath C:\Users\W9A01RG9\Desktop\Get-ExpirationDates\Errors.txt -Append
        }
    }
}
if ($sqlConnection.State -eq [Data.ConnectionState]::Open) 
{
    $sqlConnection.Close()
}
Function ADPasswordExpiration([String]$SamAccountName, [string]$dns)
{
    #Password never expires? It'll be changed anyway once per year, so we take 365 days, add it to create date and get Expiratin date!
    $wholeYear = 365 
    if($(Get-ADUser $SamAccountName -server $dns -Properties PasswordNeverExpires).PasswordNeverExpires)
    {
        $MaxPasswordAge = $wholeYear
    }
    else
    {
        $MaxPasswordAge = (Get-ADDefaultDomainPasswordPolicy -server $dns).MaxPasswordAge.TotalDays
    }
    $PasswordBeginDate = (Get-ADuser $SamAccountName -server $dns -properties *).PasswordLastSet
    $PasswordExpriyDate = ($PasswordBeginDate).AddDays($MaxPasswordAge)
    $PasswordExpired = $((Get-Date).AddDays(0) -gt $PasswordExpriyDate)
    $ADPasswordInfo = Get-ADUser -Filter {Enabled -eq $true -and SamAccountName -eq $SamAccountName} -server $dns -Properties *
    return [array]$a = $PasswordExpriyDate, $PasswordExpired, $ADPasswordInfo    
}