Do you offer a lifetime premium account?
No. FlexClip offers 3 paid plans for you:
$5.99/month (billed annually=$71.88, saving $48 every year)
$9.99/month (billed annually=$119.88, saving $120 every year)
$19.99/month (billed annually=$239.88, saving $120 every year)
All prices are in USD.
You can subscribe to a suitable plan to meet your needs, and the plan will be renewed automatically unless you cancel it.