If the bulk of revenue largely comes from finding new clients and doing big pieces of work for them (building an ecom store, website, whatever) get good at networking and sales.
Then for every client you possibly can push a SLA/recurring support for emergencies at what seems like 'not a lot' (to them) for their peace of mind and knowing you'll be available to jump on stuff for X emergency hours if needed. Most will never need it (and not at the same time) and you'll build up MRR here.
You can do very well from this, particularly with a couple of very good clients (think big corps; they need a few 'big' (not to you, but they pay good money) builds/projects a year, are happy to pay to know you're 'there' in between).
If you want to scale beyond 'you' (ie become a small agency), again, it's all in being good at sales.