I suffer very much from the same issue, although I'm not motivated by recurring revenue. I also figured out that I'm only motivated on a couple of evenings a month to really contribute to side projects.

What helped me in the past was to write down a single thing that I want to add the next time I feel motivated again and then spend the whole evening focussed on shipping that particular thing. Because I always feel motivated and focussed I can keep my attention span up for several months, previously I would totally get bored after a couple of days.