Hello,
as far as I know, you cannot extend/update the evaluation license.
After 60 days, your throughput will drop (to 2,5 MB I think).Within the 60 day period, the full feature set is supported, and there is no throughput limit, so yes, you can fully test your production traffic within the evaluation period.
After the 60 days, only the standard features are supported, all advanced features are not.