Hi Dmitry,
If it would be easier for development, it would be fine with us if there were an implementation of months rather than years. For example, if there were a possibility of up to 60 months, then we could make the interval anything from on month to 5 years.
Of course I have no way of knowing how the feature has been developed in the past, but I thought that I'd mention our thought in case it was helpful.
We need this feature, and so do others and this would seem to take care of may different requested lengths.
Best wishes on 3.3!
Joe