Hi,
once we release a new major version, we actually don't update the previous version anymore unless it is absolutely necessary (critical security related issues). We usually have a cut off day of 6 months after a new major version has been released but in this is not really a hard date and may vary depending on the severity of the critical issue.
As for the license: the license is perpetual for the major version you purchased the license for. Meaning you can use this license for as long as you want.
I hope this helps.
Regards,
Stefan
Kiruthika