The easiest scriptable way to check FS4SP certificates
Put this in a weekly script to make sure you never forget about certificates expiring.
$cert = @(dir cert:\LocalMachine\My -recurse | ? { $_.Subject -eq 'CN=FASTSearchCert' })[0]
Write-Host "Self-signed certificate expires on:"
Write-Host $cert.NotAfter -foregroundcolor "green"