No.
The eval start with the first start of ESXi and ends 60 days after that. Its not the uptime because its the period of time since first powered up.
Within these first 60 days you can switch and change between licenses but after that you cant back into Eval mode.
There is only one option to get 60 new days of eval. When ever you update your ESXi to a new major version it will automaticly go into eval mode again because during a upgrade there is no way to deploy a new license. This job have to be done as a post upgrade step.
Regards,
Joerg