Do you offer a lifetime premium account?
No. FlexClip offers 3 paid plans for you:
$4.99/month (billed annually=$59.88, saving $48 every year)
$7.99/month (billed annually=$95.88, saving $96 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.