I get burned out doing any single thing too much, so I've always mixed hiking and (until I tore my rotator cuff) kayaking in the mix.
That said, one way I've found to keep my cycling determination up currently (with lots of major charity/group rides cancelled) is to join the cyber "challenge" equivalent of the ride many of them are putting on. The Rails to Trails Conservancy
Great American Ride is one where 3 friends and I joined (late) and it is a good motivation to at least do the short boring rides since it will help move us east!
My local biking club has a similar but simpler Strava chellenge for a cancelled century ride - my miles feed that, too!
The downside: only mileage counts, not watts or climbing. So, always tempting to do the easier rides...