If the release you purchased is doing the job there's no mandate to update; it won't expire. Retain your registration info. The installer can usually be found in this path...
"C:\Program Files (x86)\NCH Software\VideoPad" (or similar, without the x86) It can also be downloaded here. Regestered reinstalls are normally no problem. But if one arises contact the company.
There's a six-month grace period during which upgrading is free. After that, unlicensed newer versions can always be test driven, to see if they often anything new of interest.