Continuity of practice is very important for cultivating jhanas. The more consistent and consecutive practice you do, the better. Concentration states are much easier to get into on retreat or at high doses of daily-life practice. There are those who, having attained real mastery, can drop into concentration states just by a gentle inclination to do so. However, for most, concentration abilities can fade quickly off-retreat, which can be a real surprise for those who are not expecting this.
