Nate I also do not do yearly rental increases, but when you hit the 5-year mark moving them from 20% under market to 12% under with plenty of notice seems reasonable.
I do know people who don’t even raise after 10 years and get to be 30-40% under market. I don’t think they are all irrational. The most common situation is that there are maintenance issues the current tenant has accepted but a new one likely wouldn’t. They might also not have the energy to deal with even a medium-maintenance tenant and don’t want to lose the money associated with a property management company.