VERY good question and I'll be interested to see wha other peeps say. Here's my answer:
1 TRY to fly once a week. Over the whole time you won't actually do it more than once a fortnight for the reasons you alluded to.
2 Establish flying as part of a family routine. For exmple, my family are more than usually supine on Sunday mornings, so my routine is to book up Sunday am slots in whatever I'm flying.
3 Establish exercises which you like doing and stay in practice with them. Take pride in doing them well. This doesn't have to be especially macho - six smart 'touch and go's' for example, a MATZ penetration, a landing out at Le2k, etc.
4 Do one new 'thing' each year, e.g., convert onto a different type, IMC, aerobatic course, etc.
5 Go back to school regularly. Fly dual with instructors regularly on exercises like VOR tracking, field landings.
6 Don't solo all the time - it gets lonely. Take passengers and share flights with pilot buddies.
Hope this helps, I think this is an important topic.