It is necessary to spend time every morning in the Greek and Hebrew, or alternate them every morning. There are many strategies or systems out there for accomplishing this diurnal discipline. But I would like to suggest something in addition to this (notice I said “in addition,” it should not be a replacement for daily absorption!).
Take one day out of the month such as, for example, choosing the first Monday of every month, and devote the entire day, from morning to sundown, to work on your Greek or Hebrew (I alternate Greek and Hebrew monthly). There is truly something to say about immersing yourself deeply for an entire day in the original language for a sustained period of time. Daily immersion is required for long term memory, indeed; but occasional (monthly) deep immersion augments that long term memory.
My routine is a suggested plan: Every other hour I just translate the text. And if it is a Greek day, the other alternate hours I will read through all of the syntax summaries in the back of Wallace’s grammar to keep the categories fresh in my mind (that is a total of six times a year). Trust me, if you have spent the time closely reading Wallace’s entire grammar from cover to cover, you will not want to forget those categories! I also review Greek verbal aspect in Porter’s works. In addition, it is good to review Greek vocabulary. For Hebrew it will be reviewing the categories from William’s Hebrew Syntax. So the emphasis is two-fold: Every other hour I simply translate the text, then the other alternate hours I review grammatical categories and vocabulary. After twelve hours of this, it will be satisfying.
For some individuals, they may want to even go back to Mounce’s grammar and review those notorious “mi” verbs, or non-indicative verbs—even re-memorize some verbal or nominal paradigms.
Don’t be a slacker! Take one day out of the month and just do it!