Realistically, it would need to be higher than 1 year of Ultra, unless it only included some of the perks of Ultra. If it was priced the same for 1 year vs Lifetime, very few users would pay for the yearly sub.
Personally, I'm happy to keep paying the monthly sub to support LJ, if the development stalls or even stops completely, I'll be stopping my subscription. I'm happy to provide continuous support for apps that I use daily if it means that the development continues.