In UTM9.1 you could create a voucher with a validity period of 3650 days, in this béta it gives the following error (even for 710 days)
The voucher definiton object requires a number in the range 0-1000000 for the validity period attribute.
Managing several Sophos UTMs and Sophos XGs both at work and at some home locations, dedicated to continuously improve IT-security and feeling well helping others with their IT-security challenges.
Sometimes I post some useful tips on my blog, see blog.pijnappels.eu/category/sophos/ for Sophos related posts.